When to use the two sample t test?

When to use the two sample t test?

Under the assumptions, this test works for small and large sample sizes (and in the case of large sample sizes will approach the z-test). The two-sample t-test makes no assumption about equal sample sizes. However, if you have 2 n observations, the beat allocation of them is into two groups, each with n observations.

How to test small and unbalanced sample sizes?

Small and unbalanced sample sizes for two groups – what to do? I have data for two groups (i.e. samples) I wish to compare but the total sample size is small (n = 29) and strongly unbalanced (n = 22 vs n = 7).

When does the t test have inflated type I error?

If the smallest sample size is the one with highest variance the test will have inflated Type I error). The Welch-Satterthwaite version of the t-test, on the other hand, does not assume equal variances. If you’re thinking of the Fisher-Pitman permutation test, it too assumes equal variances (if you want to infer unequal means from a low p-value).

Are there any t-tests that are statistically significant?

Initially a colleague ran t-tests on these data, and some were statistically significant with P<0.001, another was not significant with P=0.069. Some samples were normally distributed, others were not. Some tests involved large departures from ‘equal’ variances. I have several questions: are t-tests appropriate here? If not, why?

Two-Sample T-Test is also known as independent T-Test or between-subjects T-test. We perform this test when we want to compare the mean of two different samples. In this example, our null hypothesis i s that there is no difference between the mean score of psychology students and law students.

When to compare the mean of two samples?

We perform this test when we want to compare the mean of two different samples. In this example, our null hypothesis i s that there is no difference between the mean score of psychology students and law students. Our althernative hypothesis is that there is difference between the mean score of psychology students and law students.

What’s the difference between P and L in the t test?

Here, ‘p’ is for student doing psychology and ‘l’ is for law students. Select “Analyze -> Compare Means -> Independent-Samples T Test”. A new window pops out. From the list on the left, select the variable “Test_scores” as “Test Variable (s)” and the variable “Students” as the grouping variable.

How to compare means between two groups using SPSS?

Comparing Means between Two Groups: Performing Two-Sample T-test using SPSS Step 1. Select “Analyze -> Compare Means -> Independent-Samples T Test”. A new window pops out. Step 2. From the list on the left, select the variable “Test_scores” as “Test Variable (s)” and the variable “Students”… Step

Use of the t-test assumes that estimates are based on probability sampling or random allocation, that observations are independent, that the means are of measurement variables, and that observations are drawn from normally distributed populations. The two-sample t-test is probably the most widely used (and misused) statistical test.

How to calculate error rate for multiple t-tests?

By running two t-tests on the same data you will have increased your chance of “making a mistake” to 10%. The formula for determining the new error rate for multiple t-tests is not as simple as multiplying 5% by the number of tests. However, if you are only making a few multiple comparisons,…

Can a t test be used for multiple comparisons?

The t-test should also not be used for multiple comparisons – carrying out dozens (or hundreds) of t-tests means that Type I errors are inevitable. Using a modified alpha level reduces the problem, but it is usually far better to focus on just a few key comparisons.

When does the paired t test cannot apply?

Here’s a simple check to determine if the paired t test can apply – if one sample can have a different number of data points from the other, then the paired t test cannotapply. Examples