A logistic regression model, M1, for diabetes (Y or N) in a random sample of patients in a clinic contains the following variables: Sex (M or F) Age (continuous) BMI (continuous) Ethnic group (categorical, with 5 levels) Model M2 is the same as M 1, but with Ethnic group omitted. A likelihood ratio test is used to select between the two models. What is the degrees of freedom for the chi squared test statistic?