A physical therapist conducts a study examining the effect of implementing a group exercise program at an assisted living facility for elderly adults. One group of residents is selected to participate in the program, and a second group serves as a control. After 6 weeks, the researcher records a combined score measuring balance and strength for each individual. The data are as follows:

Control Exercise

n = 10 n = 15

M = 12 M = 15.5

SS = 120.5 SS = 190.0

If the researcher decides to use a two-tailed test at an α = .05 level, what are degrees of freedom and tcritical value?

df = 23; tcrit = ±2.069

df = 25; tcrit = ±2.060

df = 5; tcrit = ±2.571

df = 23; tcrit = ±1.714

Construct a 95% confidence interval for the difference in sample means to estimate the difference in population means.

95% CI = 0.40 to 6.6

95% CI = 10.43 to 18.07

95% CI = 5.67 to 7.76

95% CI = 0.93 to 6.07