Suppose that an observational study to see how age affects how happiness was conducted based on a random sample of 1778 individuals. Individuals were categorized into five different age groups. They were then given a questionnaire in which they were asked to rate their happiness as either happy, unhappy, or neutral. The results were tabulated in a two-way table in which the column variables were the age groups and the row variables were the happiness values.

Researchers then conducted a chi-square test for independence to see if happiness values and age groups aredependent.

How many degrees of freedom does the chi-square statistichave?