- Tweet
- Why does the standard deviation of the sample mean less
- Two Population Means with Unknown Standard Deviations
- population standard deviation unknown How to Calculate a
distributions Standard Deviation of small population
8.2 A Confidence Interval for a Population Standard. and the sample standard deviation is 0.35 days. is unknown, you estimate it with s, the sample standard deviation.) This is a job for the t-test. Because the sample size is small (n =10 is much less than 30) and the population standard deviation is not known, your test statistic has a t-distribution., Do we calculate the Standard Deviation of a population the same no matter how small (say less than 30) population size gets? Does distribution type play any roles in this? Thank you in advance.
Why do you commonly assume 0.5 when the standard deviation
When the population is normally distributed population. In practice, we rarely know the population standard deviation. In the past, when the sample size was large, this did not present a problem to statisticians. They used the sample standard deviation s as an estimate for σ and proceeded as before to calculate a confidence interval with close enough results., The 95% confidence interval states that 95% of the sample means of a specified sample size selected from a population will lie within plus and minus 1.96 standard deviations of the hypothesized population ….
In selecting the correct formula for construction of a confidence interval for a population mean ask two questions: is the population standard deviation σ known or unknown, and is the sample large or small? We can construct confidence intervals with small samples only if the population is normal. Two Population Means with Unknown Standard Deviations. Learning Outcomes . Classify hypothesis tests by type; Conduct and interpret hypothesis tests for two population means, population standard deviations unknown; The two independent samples are simple random samples from two distinct populations. For the two distinct populations: if the sample sizes are small, the distributions are …
At 4:30 of this video the author decided to estimate the standard deviation of the population with sample standard deviation (sample size was $100$). In the next video, the author mentioned that i... = required sample size, Пѓ (the Greek letter sigma) = the population standard deviation, a measure of the variation in the population (see Chapter 13) and d = the degree of precision required by the researcher. A drawback with this formula is the need to know the population standard deviation. This may be known from prior research; if a good
Comparison of Means: One Sample, Unknown Population SD It may be the case where we do NOT know the standard deviation of the population. In this case, we need to use the standard deviation of the sample (s) to estimate the standard deviation of the population (Пѓ). = required sample size, Пѓ (the Greek letter sigma) = the population standard deviation, a measure of the variation in the population (see Chapter 13) and d = the degree of precision required by the researcher. A drawback with this formula is the need to know the population standard deviation. This may be known from prior research; if a good
If the population is not normal but its standard deviation, σ is known and the sample size, n is large (n ≥ 30), z-distribution values may be used to determine interval estimates for the population mean. Two Population Means with Unknown Standard Deviations. Learning Outcomes . Classify hypothesis tests by type; Conduct and interpret hypothesis tests for two population means, population standard deviations unknown; The two independent samples are simple random samples from two distinct populations. For the two distinct populations: if the sample sizes are small, the distributions are …
At 4:30 of this video the author decided to estimate the standard deviation of the population with sample standard deviation (sample size was $100$). In the next video, the author mentioned that i... In practice, we rarely know the population standard deviation. In the past, when the sample size was large, this did not present a problem to statisticians. They used the sample standard deviation s as an estimate for Пѓ and proceeded as before to calculate a confidence interval with close enough results.
In practice, we rarely know the population standard deviation. In the past, when the sample size was large, this did not present a problem to statisticians. They used the sample standard deviation s as an estimate for \(\sigma\) and proceeded as before to calculate a … When the population is normally distributed population standard deviation s is unknown and the sample size is n equals 15 the confidence interval for the population mean s is based on the?
Do we calculate the Standard Deviation of a population the same no matter how small (say less than 30) population size gets? Does distribution type play any roles in this? Thank you in advance Use of the sample standard deviation implies that these 14 fulmars are a sample from a larger population of fulmars. If these 14 fulmars comprised the entire population (perhaps the last 14 surviving fulmars), then instead of the sample standard deviation, the calculation would use …
Use of the sample standard deviation implies that these 14 fulmars are a sample from a larger population of fulmars. If these 14 fulmars comprised the entire population (perhaps the last 14 surviving fulmars), then instead of the sample standard deviation, the calculation would use … This fact is then used to construct confidence intervals for the population mean based on teh standard normal distribution. However in most prectical situations the value of the standard deviation is unknown and we use a sample estimate to scale since we can't use a known value. Under the same assumptions about the sample distribution the
distributions Standard Deviation of small population
Why does the standard deviation of the sample mean less. 02/11/2015 · Sample size for known population, unknown standard deviation, simple "yes/no" response survey (self.AskStatistics) submitted 3 years ago by Whos_doin_what_now Hi all, probably a simple question but it's been years since I studied statistics and my internet searching is turning up lots of calculators but none seem to be what I'm after., Use of the sample standard deviation implies that these 14 fulmars are a sample from a larger population of fulmars. If these 14 fulmars comprised the entire population (perhaps the last 14 surviving fulmars), then instead of the sample standard deviation, the calculation would use ….
Why does the standard deviation of the sample mean less. When the population is normally distributed population standard deviation s is unknown and the sample size is n equals 15 the confidence interval for the population mean s is based on the?, The 95% confidence interval states that 95% of the sample means of a specified sample size selected from a population will lie within plus and minus 1.96 standard deviations of the hypothesized population ….
Stats Final Probability Flashcards Quizlet
Stats Final Probability Flashcards Quizlet. Use of the sample standard deviation implies that these 14 fulmars are a sample from a larger population of fulmars. If these 14 fulmars comprised the entire population (perhaps the last 14 surviving fulmars), then instead of the sample standard deviation, the calculation would use … At 4:30 of this video the author decided to estimate the standard deviation of the population with sample standard deviation (sample size was $100$). In the next video, the author mentioned that i....
The 95% confidence interval states that 95% of the sample means of a specified sample size selected from a population will lie within plus and minus 1.96 standard deviations of the hypothesized population … Two Population Means with Unknown Standard Deviations. Learning Outcomes . Classify hypothesis tests by type; Conduct and interpret hypothesis tests for two population means, population standard deviations unknown; The two independent samples are simple random samples from two distinct populations. For the two distinct populations: if the sample sizes are small, the distributions are …
Hypothesis Testing: Unknown Population Standard Deviation. Return to the Main Math 160 Chapter 9 Topics page Revised November, 2014 Some images on this page have been generated via … The 95% confidence interval states that 95% of the sample means of a specified sample size selected from a population will lie within plus and minus 1.96 standard deviations of the hypothesized population …
An unknown distribution has a mean of 80 and a standard deviation of 12. A sample size of 95 is drawn randomly from the population. Find the probability that the sum of the 95 values is less than 7,200. Use of the sample standard deviation implies that these 14 fulmars are a sample from a larger population of fulmars. If these 14 fulmars comprised the entire population (perhaps the last 14 surviving fulmars), then instead of the sample standard deviation, the calculation would use …
Before we saw that as the sample size increased the standard deviation of the sampling distribution decreases. This was why we choose the sample mean from a large sample as compared to a small sample, all other things held constant. Thus far we assumed that we knew the population standard deviation. This will virtually never be the case. and the sample standard deviation is 0.35 days. is unknown, you estimate it with s, the sample standard deviation.) This is a job for the t-test. Because the sample size is small (n =10 is much less than 30) and the population standard deviation is not known, your test statistic has a t-distribution.
Do we calculate the Standard Deviation of a population the same no matter how small (say less than 30) population size gets? Does distribution type play any roles in this? Thank you in advance and the sample standard deviation is 0.35 days. is unknown, you estimate it with s, the sample standard deviation.) This is a job for the t-test. Because the sample size is small (n =10 is much less than 30) and the population standard deviation is not known, your test statistic has a t-distribution.
If the samples are related (for example, you are comparing the answers of husbands and wives, or identical twins), you should use a t-test for paired samples instead. What if the population standard deviations are known? The main purpose of this calculator is for comparing two population mean when sigma is unknown for both populations. 02/11/2015В В· Sample size for known population, unknown standard deviation, simple "yes/no" response survey (self.AskStatistics) submitted 3 years ago by Whos_doin_what_now Hi all, probably a simple question but it's been years since I studied statistics and my internet searching is turning up lots of calculators but none seem to be what I'm after.
If the population is not normal but its standard deviation, σ is known and the sample size, n is large (n ≥ 30), z-distribution values may be used to determine interval estimates for the population mean. The 95% confidence interval states that 95% of the sample means of a specified sample size selected from a population will lie within plus and minus 1.96 standard deviations of the hypothesized population …
In practice, we rarely know the population standard deviation. In the past, when the sample size was large, this did not present a problem to statisticians. They used the sample standard deviation s as an estimate for \(\sigma\) and proceeded as before to calculate a … Really no reason other than convention. With respect to differences in means Cohen described standardized differences in means of .2, .5, and .8 as small, medium, and large effects, respectively. Effect size SHOULD be determined based on substanti...
In this case we don't need the population standard deviation \(\sigma\) to be known, and we can use instead the sample standard deviation \(s\). Other Calculators you can use In case the population standard deviation is known, you can use this confidence interval calculator for a population means when the population standard deviation is known . • Population standard deviation is calculated when all the data regarding each individual of the population is known. Else, the sample standard deviation is calculated. • Population standard deviation is given by σ = √{ ∑(xi-µ) 2 / n} where µ is the population mean and n is the population size but the sample standard deviation is
Two Population Means with Unknown Standard Deviations
probability When standard deviation is unknown. A sample is a part of a population that is used to describe the characteristics (e.g. mean or standard deviation) of the whole population. The size of a sample can be less than 1%, or 10%, or 60% of the population, but it is never the whole population. Population vs. Sample Variance and Standard Deviation, Two Population Means with Unknown Standard Deviations. Learning Outcomes . Classify hypothesis tests by type; Conduct and interpret hypothesis tests for two population means, population standard deviations unknown; The two independent samples are simple random samples from two distinct populations. For the two distinct populations: if the sample sizes are small, the distributions are ….
Stats Final Probability Flashcards Quizlet
8.2 A Confidence Interval for a Population Standard. At 4:30 of this video the author decided to estimate the standard deviation of the population with sample standard deviation (sample size was $100$). In the next video, the author mentioned that i..., In selecting the correct formula for construction of a confidence interval for a population mean ask two questions: is the population standard deviation Пѓ known or unknown, and is the sample large or small? We can construct confidence intervals with small samples only if the population is normal..
The Greek letter sigma, expressed as Пѓ, is the standard deviation of the population that we are studying. In using this formula we are assuming that we know what this standard deviation is. In practice we may not necessarily know for certain what the population standard deviation really is. Fortunately there are some ways around this, such as In selecting the correct formula for construction of a confidence interval for a population mean ask two questions: is the population standard deviation Пѓ known or unknown, and is the sample large or small? We can construct confidence intervals with small samples only if the population is normal.
In practice, we rarely know the population standard deviation. In the past, when the sample size was large, this did not present a problem to statisticians. They used the sample standard deviation s as an estimate for Пѓ and proceeded as before to calculate a confidence interval with close enough results. At 4:30 of this video the author decided to estimate the standard deviation of the population with sample standard deviation (sample size was $100$). In the next video, the author mentioned that i...
The Greek letter sigma, expressed as Пѓ, is the standard deviation of the population that we are studying. In using this formula we are assuming that we know what this standard deviation is. In practice we may not necessarily know for certain what the population standard deviation really is. Fortunately there are some ways around this, such as This fact is then used to construct confidence intervals for the population mean based on teh standard normal distribution. However in most prectical situations the value of the standard deviation is unknown and we use a sample estimate to scale since we can't use a known value. Under the same assumptions about the sample distribution the
The standard deviation of the sample does not “mean less” than the standard deviation of the population. They just mean different things. Perhaps you mean “why does the standard deviation of the sample tend to be smaller than that of the populatio... Comparison of Means: One Sample, Unknown Population SD It may be the case where we do NOT know the standard deviation of the population. In this case, we need to use the standard deviation of the sample (s) to estimate the standard deviation of the population (σ).
and the sample standard deviation is 0.35 days. is unknown, you estimate it with s, the sample standard deviation.) This is a job for the t-test. Because the sample size is small (n =10 is much less than 30) and the population standard deviation is not known, your test statistic has a t-distribution. Do we calculate the Standard Deviation of a population the same no matter how small (say less than 30) population size gets? Does distribution type play any roles in this? Thank you in advance
and the sample standard deviation is 0.35 days. is unknown, you estimate it with s, the sample standard deviation.) This is a job for the t-test. Because the sample size is small (n =10 is much less than 30) and the population standard deviation is not known, your test statistic has a t-distribution. Before we saw that as the sample size increased the standard deviation of the sampling distribution decreases. This was why we choose the sample mean from a large sample as compared to a small sample, all other things held constant. Thus far we assumed that we knew the population standard deviation. This will virtually never be the case.
In practice, we rarely know the population standard deviation. In the past, when the sample size was large, this did not present a problem to statisticians. They used the sample standard deviation s as an estimate for \(\sigma\) and proceeded as before to calculate a … When the population is normally distributed population standard deviation s is unknown and the sample size is n equals 15 the confidence interval for the population mean s is based on the?
This fact is then used to construct confidence intervals for the population mean based on teh standard normal distribution. However in most prectical situations the value of the standard deviation is unknown and we use a sample estimate to scale since we can't use a known value. Under the same assumptions about the sample distribution the A sample is a part of a population that is used to describe the characteristics (e.g. mean or standard deviation) of the whole population. The size of a sample can be less than 1%, or 10%, or 60% of the population, but it is never the whole population. Population vs. Sample Variance and Standard Deviation
Do we calculate the Standard Deviation of a population the same no matter how small (say less than 30) population size gets? Does distribution type play any roles in this? Thank you in advance Use of the sample standard deviation implies that these 14 fulmars are a sample from a larger population of fulmars. If these 14 fulmars comprised the entire population (perhaps the last 14 surviving fulmars), then instead of the sample standard deviation, the calculation would use …
• Population standard deviation is calculated when all the data regarding each individual of the population is known. Else, the sample standard deviation is calculated. • Population standard deviation is given by σ = √{ ∑(xi-µ) 2 / n} where µ is the population mean and n is the population size but the sample standard deviation is A sample is a part of a population that is used to describe the characteristics (e.g. mean or standard deviation) of the whole population. The size of a sample can be less than 1%, or 10%, or 60% of the population, but it is never the whole population. Population vs. Sample Variance and Standard Deviation
When the population is normally distributed population standard deviation s is unknown and the sample size is n equals 15 the confidence interval for the population mean s is based on the? 31/03/2013В В· This video will help you out to find the sample size from a population when the standard deviation is unknown.
If the population is not normal but its standard deviation, σ is known and the sample size, n is large (n ≥ 30), z-distribution values may be used to determine interval estimates for the population mean. 31/03/2013 · This video will help you out to find the sample size from a population when the standard deviation is unknown.
• Population standard deviation is calculated when all the data regarding each individual of the population is known. Else, the sample standard deviation is calculated. • Population standard deviation is given by σ = √{ ∑(xi-µ) 2 / n} where µ is the population mean and n is the population size but the sample standard deviation is = required sample size, σ (the Greek letter sigma) = the population standard deviation, a measure of the variation in the population (see Chapter 13) and d = the degree of precision required by the researcher. A drawback with this formula is the need to know the population standard deviation. This may be known from prior research; if a good
In this case we don't need the population standard deviation \(\sigma\) to be known, and we can use instead the sample standard deviation \(s\). Other Calculators you can use In case the population standard deviation is known, you can use this confidence interval calculator for a population means when the population standard deviation is known . Two Population Means with Unknown Standard Deviations. Learning Outcomes . Classify hypothesis tests by type; Conduct and interpret hypothesis tests for two population means, population standard deviations unknown; The two independent samples are simple random samples from two distinct populations. For the two distinct populations: if the sample sizes are small, the distributions are …
If the population is not normal but its standard deviation, σ is known and the sample size, n is large (n ≥ 30), z-distribution values may be used to determine interval estimates for the population mean. The Greek letter sigma, expressed as σ, is the standard deviation of the population that we are studying. In using this formula we are assuming that we know what this standard deviation is. In practice we may not necessarily know for certain what the population standard deviation really is. Fortunately there are some ways around this, such as
The 95% confidence interval states that 95% of the sample means of a specified sample size selected from a population will lie within plus and minus 1.96 standard deviations of the hypothesized population … The Greek letter sigma, expressed as σ, is the standard deviation of the population that we are studying. In using this formula we are assuming that we know what this standard deviation is. In practice we may not necessarily know for certain what the population standard deviation really is. Fortunately there are some ways around this, such as
8.2 A Confidence Interval for a Population Standard. Two Population Means with Unknown Standard Deviations. Learning Outcomes . Classify hypothesis tests by type; Conduct and interpret hypothesis tests for two population means, population standard deviations unknown; The two independent samples are simple random samples from two distinct populations. For the two distinct populations: if the sample sizes are small, the distributions are …, In this case we don't need the population standard deviation \(\sigma\) to be known, and we can use instead the sample standard deviation \(s\). Other Calculators you can use In case the population standard deviation is known, you can use this confidence interval calculator for a population means when the population standard deviation is known ..
Estimating population standard deviation with sample
Confidence Intervals for One Standard Deviation Using. The standard deviation of the sample does not “mean less” than the standard deviation of the population. They just mean different things. Perhaps you mean “why does the standard deviation of the sample tend to be smaller than that of the populatio..., The Greek letter sigma, expressed as σ, is the standard deviation of the population that we are studying. In using this formula we are assuming that we know what this standard deviation is. In practice we may not necessarily know for certain what the population standard deviation really is. Fortunately there are some ways around this, such as.
Solved An Unknown Distribution Has A Mean Of 80 And A Sta. A sample is a part of a population that is used to describe the characteristics (e.g. mean or standard deviation) of the whole population. The size of a sample can be less than 1%, or 10%, or 60% of the population, but it is never the whole population. Population vs. Sample Variance and Standard Deviation, The 95% confidence interval states that 95% of the sample means of a specified sample size selected from a population will lie within plus and minus 1.96 standard deviations of the hypothesized population ….
distributions Standard Deviation of small population
c8-10 stat Flashcards Quizlet. Confidence Intervals for One Standard Deviation using Standard Deviation procedure window by expanding Variances, then clicking on One Standard Deviation, and then clicking on Confidence Intervals for One Standard Deviation using Standard Deviation. You may then make the appropriate entries as listed below, or open Example 1 by going to the File = required sample size, Пѓ (the Greek letter sigma) = the population standard deviation, a measure of the variation in the population (see Chapter 13) and d = the degree of precision required by the researcher. A drawback with this formula is the need to know the population standard deviation. This may be known from prior research; if a good.
A sample is a part of a population that is used to describe the characteristics (e.g. mean or standard deviation) of the whole population. The size of a sample can be less than 1%, or 10%, or 60% of the population, but it is never the whole population. Population vs. Sample Variance and Standard Deviation The Standard deviation of the sampling distribution is further affected by two things, the standard deviation of the population and the sample size we chose for our data. Here we wish to examine the effects of each of the choices we have made on the calculated confidence interval, the confidence level and the sample size.
02/11/2015В В· Sample size for known population, unknown standard deviation, simple "yes/no" response survey (self.AskStatistics) submitted 3 years ago by Whos_doin_what_now Hi all, probably a simple question but it's been years since I studied statistics and my internet searching is turning up lots of calculators but none seem to be what I'm after. Do we calculate the Standard Deviation of a population the same no matter how small (say less than 30) population size gets? Does distribution type play any roles in this? Thank you in advance
Hypothesis Testing: Unknown Population Standard Deviation. Return to the Main Math 160 Chapter 9 Topics page Revised November, 2014 Some images on this page have been generated via … Comparison of Means: One Sample, Unknown Population SD It may be the case where we do NOT know the standard deviation of the population. In this case, we need to use the standard deviation of the sample (s) to estimate the standard deviation of the population (σ).
• Population standard deviation is calculated when all the data regarding each individual of the population is known. Else, the sample standard deviation is calculated. • Population standard deviation is given by σ = √{ ∑(xi-µ) 2 / n} where µ is the population mean and n is the population size but the sample standard deviation is In practice, we rarely know the population standard deviation. In the past, when the sample size was large, this did not present a problem to statisticians. They used the sample standard deviation s as an estimate for σ and proceeded as before to calculate a confidence interval with close enough results.
The 95% confidence interval states that 95% of the sample means of a specified sample size selected from a population will lie within plus and minus 1.96 standard deviations of the hypothesized population … Confidence Intervals for One Standard Deviation using Standard Deviation procedure window by expanding Variances, then clicking on One Standard Deviation, and then clicking on Confidence Intervals for One Standard Deviation using Standard Deviation. You may then make the appropriate entries as listed below, or open Example 1 by going to the File
If the samples are related (for example, you are comparing the answers of husbands and wives, or identical twins), you should use a t-test for paired samples instead. What if the population standard deviations are known? The main purpose of this calculator is for comparing two population mean when sigma is unknown for both populations. Do we calculate the Standard Deviation of a population the same no matter how small (say less than 30) population size gets? Does distribution type play any roles in this? Thank you in advance
31/03/2013В В· This video will help you out to find the sample size from a population when the standard deviation is unknown. Part 3 shows you how to determine the appropriate sample size for a given confidence interval and width, given that you know the population standard deviation. Sample question: Suppose we want to know the average age of an Florida State College student, plus or minus 0.5 years.
In practice, we rarely know the population standard deviation. In the past, when the sample size was large, this did not present a problem to statisticians. They used the sample standard deviation s as an estimate for σ and proceeded as before to calculate a confidence interval with close enough results. Two Population Means with Unknown Standard Deviations. Learning Outcomes . Classify hypothesis tests by type; Conduct and interpret hypothesis tests for two population means, population standard deviations unknown; The two independent samples are simple random samples from two distinct populations. For the two distinct populations: if the sample sizes are small, the distributions are …
If the population is not normal but its standard deviation, σ is known and the sample size, n is large (n ≥ 30), z-distribution values may be used to determine interval estimates for the population mean. If the population is not normal but its standard deviation, σ is known and the sample size, n is large (n ≥ 30), z-distribution values may be used to determine interval estimates for the population mean.
The standard deviation of the sample does not “mean less” than the standard deviation of the population. They just mean different things. Perhaps you mean “why does the standard deviation of the sample tend to be smaller than that of the populatio... Do we calculate the Standard Deviation of a population the same no matter how small (say less than 30) population size gets? Does distribution type play any roles in this? Thank you in advance
• Population standard deviation is calculated when all the data regarding each individual of the population is known. Else, the sample standard deviation is calculated. • Population standard deviation is given by σ = √{ ∑(xi-µ) 2 / n} where µ is the population mean and n is the population size but the sample standard deviation is At 4:30 of this video the author decided to estimate the standard deviation of the population with sample standard deviation (sample size was $100$). In the next video, the author mentioned that i...
At 4:30 of this video the author decided to estimate the standard deviation of the population with sample standard deviation (sample size was $100$). In the next video, the author mentioned that i... In selecting the correct formula for construction of a confidence interval for a population mean ask two questions: is the population standard deviation Пѓ known or unknown, and is the sample large or small? We can construct confidence intervals with small samples only if the population is normal.
and the sample standard deviation is 0.35 days. is unknown, you estimate it with s, the sample standard deviation.) This is a job for the t-test. Because the sample size is small (n =10 is much less than 30) and the population standard deviation is not known, your test statistic has a t-distribution. 02/11/2015В В· Sample size for known population, unknown standard deviation, simple "yes/no" response survey (self.AskStatistics) submitted 3 years ago by Whos_doin_what_now Hi all, probably a simple question but it's been years since I studied statistics and my internet searching is turning up lots of calculators but none seem to be what I'm after.
The 95% confidence interval states that 95% of the sample means of a specified sample size selected from a population will lie within plus and minus 1.96 standard deviations of the hypothesized population … At 4:30 of this video the author decided to estimate the standard deviation of the population with sample standard deviation (sample size was $100$). In the next video, the author mentioned that i...
Two Population Means with Unknown Standard Deviations. Learning Outcomes . Classify hypothesis tests by type; Conduct and interpret hypothesis tests for two population means, population standard deviations unknown; The two independent samples are simple random samples from two distinct populations. For the two distinct populations: if the sample sizes are small, the distributions are … The standard deviation of the sample does not “mean less” than the standard deviation of the population. They just mean different things. Perhaps you mean “why does the standard deviation of the sample tend to be smaller than that of the populatio...
31/03/2013В В· This video will help you out to find the sample size from a population when the standard deviation is unknown. The Standard deviation of the sampling distribution is further affected by two things, the standard deviation of the population and the sample size we chose for our data. Here we wish to examine the effects of each of the choices we have made on the calculated confidence interval, the confidence level and the sample size.
This fact is then used to construct confidence intervals for the population mean based on teh standard normal distribution. However in most prectical situations the value of the standard deviation is unknown and we use a sample estimate to scale since we can't use a known value. Under the same assumptions about the sample distribution the If the samples are related (for example, you are comparing the answers of husbands and wives, or identical twins), you should use a t-test for paired samples instead. What if the population standard deviations are known? The main purpose of this calculator is for comparing two population mean when sigma is unknown for both populations.