Do you use equal variance assumed or not assumed?
Do you use equal variance assumed or not assumed?
If the variances are relatively equal, that is one sample variance is no larger than twice the size of the other, then you can assume equal variances.
What is equal variance assumed and not assumed?
When equal variances are assumed, the calculation uses pooled variances; when equal variances cannot be assumed, the calculation utilizes un-pooled variances and a correction to the degrees of freedom.
What does it mean if equal variances are assumed?
The assumption of equal variances (i.e. assumption of homoscedasticity) assumes that different samples have the same variance, even if they came from different populations. The assumption is found in many statistical tests, including Analysis of Variance (ANOVA) and Student’s T-Test.
What is the difference between equal variance 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.
Why is equal variance important?
It is important because it is a formal requirement for statistical analyses such as ANOVA or the Student’s t-test. The unequal variance doesn’t have much impact on ANOVA if the data sets have equal sample sizes.
How do you assess equal variance assumption?
There are two ways to test if this assumption is met:
- Use the rule of thumb ratio. As a rule of thumb, if the ratio of the larger variance to the smaller variance is less than 4, then we can assume the variances are approximately equal and use the two sample t-test.
- Perform an F-test.
How do you know if variances are equal?
If the variances are equal, the ratio of the variances will equal 1. For example, if you had two data sets with a sample 1 (variance of 10) and a sample 2 (variance of 10), the ratio would be 10/10 = 1. You always test that the population variances are equal when running an F Test.
How do you know if variances are equal or unequal?
Use the Variance Rule of Thumb. As a rule of thumb, if the ratio of the larger variance to the smaller variance is less than 4 then we can assume the variances are approximately equal and use the Student’s t-test.
How would you know if your data have equal variances?
If the p-value is larger than the alpha level, then you can say that the null hypothesis stands — that the variances are equal; if the p-value is smaller than the alpha level, then the implication is that the variances are unequal.
How do you know if you have equal variances?
What is Levene’s test for equality of variances in SPSS?
Levene’s test of equality of variances is used to assess homogeneity of variance. Levene’s Test of Equality of Variances is used in SPSS to assess meeting the statistical assumption of homogeneity of variance in between-subjects designs. Levene’s Test of Equality of Variances is a simple statistical test to interpret.
