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Which t-test is primarily used for the comparison of the same sample tested at different times?
dependent-samples t test
The dependent-samples t test (sometimes called the paired-samples t test) is used to compare two means for the same sample tested at two different times or under two different conditions. This comparison is appropriate for pretest-posttest designs or within-subjects experiments.
Which t-test is used for comparison?
A paired samples t-test is used to compare two related means. It tests the null hypothesis that the difference between two related means is 0.
Is the t test always correct to compare means?
A frequent error is to use statistical tests that assume a normal distribution on data that are actually skewed. As mentioned above, we can not always use Student’s t test to compare means. There are different types of t-test : one-sample t test, the independent two samples t test and the paired t test.
When to use a paired or two sample t test?
If you are studying one group, use a paired t-test to compare the group mean over time or after an intervention, or use a one-sample t-test to compare the group mean to a standard value. If you are studying two groups, use a two-sample t-test. If you want to know only whether a difference exists, use a two-tailed test.
Can a t test be used for more than two groups?
A t-test should not be used to measure differences among more than two groups, because the error structure for a t-test will underestimate the actual error when many groups are being compared. If you want to compare the means of several groups at once, it’s best to use another statistical test such as ANOVA or a post-hoc test.
When to use the Student’s t-test?
When we want to compare the means of two independent groups, we can choose between using two different tests: Student’s t-test: this test assumes that both groups of data are sampled from populations that follow a normal distribution and that both populations have the same variance.