Write a question about the following article: There were 13,324 households of which 27.8% had children under the age of 18 living with them, 47.0% were Marriage living together, 10.3% had a female householder with no husband present, 4.3% had a male householder with no wife present, and 38.4% were non-families. 30.2% of all households were made up of individuals and 12.8% had someone living alone who was 65 years of age or older. The average household size was 2.32 and the average family size was 2.87.
Which groups in average are under 4 in size?