A University Wants to Compare Out-Of-State Applicants' Mean SAT Math

Multiple Choice

A university wants to compare out-of-state applicants' mean SAT math scores (μ₁) to in-state applicants; mean SAT math scores (μ₂) . The university looks at 35 in-state applicants and 35 out-of-state applicants. The mean SAT math score for in-state applicants was 540, with a standard deviation of 20. The mean SAT math score for out-of-state applicants was 555, with a standard deviation of 25. It is reasonable to assume the corresponding population standard deviations are equal. To calculate the confidence interval for the difference μ₁ - μ₂, what is the number of degrees of freedom of the appropriate probability distribution?

A) 64
B) 64.87
C) 68
D) 69