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Does a paired t-test have equal variance?
A paired t-test is designed to compare the means of the same group or item under two separate scenarios. In an unpaired t-test, the variance between groups is assumed to be equal. In a paired t-test, the variance is not assumed to be equal.
Is a two sample t-test the same as a paired t-test?
Two-sample t-test is used when the data of two samples are statistically independent, while the paired t-test is used when data is in the form of matched pairs. To use the two-sample t-test, we need to assume that the data from both samples are normally distributed and they have the same variances.
What does variance mean in a paired t-test?
The paired t test provides an hypothesis test of the difference between population means for a pair of random samples whose differences are approximately normally distributed. – where d bar is the mean difference, s² is the sample variance, n is the sample size and t is a Student t quantile with n-1 degrees of freedom.
What does two sample equal variance mean?
The Two-Sample assuming Equal Variances test is used when you know (either through the question or you have analyzed the variance in the data) that the variances are the same. The Two-Sample assuming UNequal Variances test is used when either: You know the variances are not the same.
When to use a paired t test?
The paired t-test is used when the variable is numerical in nature (for example, the height of a person or the weight of a person) and the individuals in the sample are either paired up in some way (such as a husband and wife) or the same people are used twice (for example, preprocedure and postprocedure).
What is an example of a paired t test?
The paired sample t-test is also called dependent sample t-test. It’s an univariate test that tests for a significant difference between 2 related variables. An example of this is if you where to collect the blood pressure for an individual before and after some treatment, condition, or time point.
What is an example of a single sample t test?
A single sample t-test (or one sample t-test) is used to compare the mean of a single sample of scores to a known or hypothetical population mean. So, for example, it could be used to determine whether the mean diastolic blood pressure of a particular group differs from 85, a value determined by a previous study.
What is an example of a t test?
Example: Independent samples T test when variances are not equal Problem Statement. In our sample dataset, students reported their typical time to run a mile, and whether or not they were an athlete. Before the Test. Before running the Independent Samples t Test, it is a good idea to look at descriptive statistics and graphs to get an idea of what to expect. Running the Test. Output. Decision and Conclusions.