What does equal variance mean in t test?

Statistical tests, such as analysis of variance (ANOVA), assume that although different samples can come from populations with different means, they have the same variance. Equal variances (homoscedasticity) is when the variances are approximately the same across the samples.

Does two-sample t test assume equal variance?

The t-Test Paired Two-Sample for Means tool performs a paired two-sample Student’s t-Test to ascertain if the null hypothesis (means of two populations are equal) can be accepted or rejected. This test does not assume that the variances of both populations are equal.

What test to use if variances are equal?

Levene’s test ( Levene 1960) is used to test if k samples have equal variances. Equal variances across samples is called homogeneity of variance. Some statistical tests, for example the analysis of variance, assume that variances are equal across groups or samples. The Levene test can be used to verify that assumption.

Which t test is equal or UNequal variance?

Welch’s t-test
Welch’s t-test: Assumes that both groups of data are sampled from populations that follow a normal distribution, but it does not assume that those two populations have the same variance. So, if the two samples do not have equal variance then it’s best to use the Welch’s t-test.

What is unequal variance t test?

For the unequal variance t test, the null hypothesis is that the two population means are the same but the two population variances may differ. The unequal variance t test reports a confidence interval for the difference between two means that is usable even if the standard deviations differ.

What does the t test for the difference between the means of 2 independent populations assume?

The t test for the difference between the means of two independent samples assumes that the respective: In testing for differences between the means of two independent populations the null hypothesis states that: the difference between the two population means is not significantly different from zero.

How do you test for unequal variances?

How the unequal variance t test is computed

1. Calculation of the standard error of the difference between means. The t ratio is computed by dividing the difference between the two sample means by the standard error of the difference between the two means.
2. Calculation of the df.

What is Bartlett test for equal variances?

Bartlett’s test of Homogeneity of Variances is a test to identify whether there are equal variances of a continuous or interval-level dependent variable across two or more groups of a categorical, independent variable. It tests the null hypothesis of no difference in variances between the groups.

What is a two-sample unequal variance t test?

In statistics, Welch’s t-test, or unequal variances t-test, is a two-sample location test which is used to test the hypothesis that two populations have equal means.

What is meant by equal and unequal variance?

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.

What is the test statistic for an independent samples t test?

The test statistic for an Independent Samples t Test is denoted t. There are actually two forms of the test statistic for this test, depending on whether or not equal variances are assumed. SPSS produces both forms of the test, so both forms of the test are described here.

What are the basic assumptions of a two-sample equal-variance t-test?

When running a two-sample equal-variance t-test, the basic assumptions are that the distributions of the two populations are normal, and that the variances of the two distributions are the same.

Do the samples have equal variances?

HA: The samples do not have equal variances. where s12 and s22 are the sample variances. If the p-value that corresponds to the test statistic is less than some significance level (like 0.05), then we have sufficient evidence to say that the samples do not have equal variances.

How to test for homogeneity of variance in independent samples?

Recall that the independent samples T test requires the assumption of homogeneity of variance — i.e., both groups have the same variance. SPSS conveniently includes a test for the homogeneity of variance, called Levene’s Test, whenever you run an independent samples T test.