I am using Tweedie GLM as my data contains exact zeroes. However, my stats is weak and want to confirm a few things.
- Does Tweedie GLM assume normality of residuals?
- Is shapiro.test() the way for finding normality of residuals for a model with Tweedie GLM?
- If the data was not normally distributed nor were the residuals can I use "glht" function for post hoc analyses?
here is the code:
require(statmod) require(tweedie) c0 <- tweedie.profile(y~x, data = c, p.vec = seq(1.0, 2.0, 0.01), method = "series") c0$p.max c1 <- glm(y~x, data = c, family = tweedie(var.power = 1.11, link.power = 0)) summary(c1) shapiro.test(residuals(c1)) Shapiro-Wilk normality test data: residuals(c1) W = 0.81176, p-value < 2.2e-16
Residuals are not normal.
- Is the code correct?
- Is Tweedie GLM one of the options for a dataset as mine?
Any suggestions welcome. Thanks.