spaMM (version 4.5.0)

seeds: Seed germination data

Description

A classic toy data set, “from research conducted by microbiologist Dr P. Whitney of Surrey University. A batch of tiny seeds is brushed onto a plate covered with a certain extract at a given dilution. The numbers of germinated and ungerminated seeds are subsequently counted” (Crowder, 1978). Two seed types and two extracts are here considered in a 2x2 factorial design.

Usage

data("seeds")

Format

The data frame includes 21 observations on the following variables:

plate

Factor for replication;

seed

Seed type, a factor with two levels O73 and O75;

extract

Root extract, a factor with two levels Bean and Cucumber;

r

Number of seeds that germinated;

n

Total number of seeds tested

References

Crowder, M.J., 1978. Beta-binomial anova for proportions. Appl. Statist., 27, 34-37.

Y. Lee and J. A. Nelder. 1996. Hierarchical generalized linear models (with discussion). J. R. Statist. Soc. B, 58: 619-678.

Examples

# An extended quasi-likelihood (EQL) fit as considered by Lee & Nelder (1996):
data("seeds") 
fitme(cbind(r,n-r)~seed*extract+(1|plate),family=binomial(),
      rand.family=Beta(),
      method="EQL-", # see help("method") for difference with "EQL+" method
      data=seeds)