Question

We wish to study the effect of drought stress on height growth of red maple seedlings. The factors of interest are the amount of stress and variety of tree. Stress is at two levels: no stress (that is, always well watered) and drought-stressed after 6 weeks of being well watered. There are four red maple varieties available, and all individuals within a given variety are clones, that is, genetically identical.

- The line of R code you would use to fit the model to the data.

Answer 1

Let the variables height, stress and maple denote height growth, stress levels and red maple varieties respectively.

stress = 0 for No Stress

stress = 1 for drought-stressed

Four red maple varieties are denoted with values maple = 0, 1, 2, 3

R code you would use to fit the model to the data is,

model = lm(height ~ stress + maple)