What is an intercept variable?
The intercept (often labeled the constant) is the expected mean value of Y when all X=0. Start with a regression equation with one predictor, X. If X sometimes equals 0, the intercept is simply the expected mean value of Y at that value.
What is categorical frequency?
Counting on the frequency One way to summarize categorical data is to simply count, or tally up, the number of individuals that fall into each category. The number of individuals in any given category is called the frequency (or count) for that category.
When to use the intercept in a model?
If you have dummy variables in your model, though, the intercept has more meaning. Dummy coded variables have values of 0 for the reference group and 1 for the comparison group. Since the intercept is the expected mean value when X=0, it is the mean value only for the reference group (when all other X=0).
What is the intercept of the response variable?
Thus, in your case, the intercept is the mean level of the response variable for those in the reference level of SMOKE, which I suspect are smokers. My reasoning here is that your variable is SMOKE, and the non-reference-level is labeled SMOKEN, which I am interpreting as SMOKE-“no”.
Which is the reference level of the categorical variable?
This means that one level of the categorical variable will be considered the reference level, and will be coded as 0. The other level will be coded as 1. Thus, in your case, the intercept is the mean level of the response variable for those in the reference level of SMOKE, which I suspect are smokers.
What are the effects of a categorical variable?
When a categorical variable contains all possible levels of interest, the effects for these levels are called fixed effects. When a categorical variable contains a sample of all possible levels of interest, the effects are random effects. These sampled levels are considered independent samples of an ” unobserved variable “.