evrot: Rule of Thumb calculation for equal variances.

In clayford/dvdata: Data Files for Design and Analysis of Experiments (Dean & Voss)

Description

evrot calculates the variance of your response (or dependent) variable for each level of your treatment (or independent) variable, and then calculates the ratio of the maximum variance to minimum variance. A rule of thumb is that if this ratio exceeds three, the assumption of constant variance may be violated.

Usage

evrot(resp, trt)

Arguments

resp	The dependent variable or response.
trt	The treatment or independent variable. Must be a factor.

Value

The ratio of maximum variance to the minimum variance of resp by trt.

Examples

g <- gl(n = 4,k = 10)
d <- rnorm(4*10, mean = rep(1:4,each=10), sd=1)
evrot(resp = d, trt = g)

with(balloon, evrot(TIME, COLOR))

clayford/dvdata documentation built on May 13, 2019, 7:38 p.m.