Research Is Conducted Regarding the Average Age at Retirement for Four

Multiple Choice

Research is conducted regarding the average age at retirement for four career groups.To test whether there is a relationship between age of retirement and career in these groups,700 employees,recently retired,are randomly selected.The resulting data are displayed in the contingency table below.
How many degrees of freedom are there for the chi-square test statistic?

A) 12
B) 9
C) 16
D) 20
E) 25