Dispersion Tests
Chi-Square Test for Variance#

Description#
Determines if the variance of a population is equal to a specified value.
Tail | Alt. Hypothesis |
---|
left | H1:σ2<σ02 |
right | H1:σ2>σ02 |
both | H1:σ2=σ02 |
Returns#
- p-value
- decision
- Chi-Sq statistic
F-Test for Two Variances#

Description#
Determines if the variances of two populations are equal.
Tail | Alt. Hypothesis |
---|
left | H1:σ12<σ22 |
right | H1:σ12>σ22 |
both | H1:σ12=σ22 |
Returns#
- p-value
- decision
- F statistic
Levene Test for Equal Variances#

Description#
Null hypothesis is that the population variances are equal.
The Levene test statistic is defined as:
W=(k−1)(N−k)∑i=1k∑j=1Ni(Zij−Zˉi.)2∑i=1kNi(Zˉi.−Zˉ..)2
where Zij=∣Yij−Yˉi.∣ and Yˉi. is the mean of the ith subgroup.
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Often used to check the homogeneity of variances assumption before running an ANOVA.
Returns#
- p-value
- decision
- F statistic
- degrees of freedom