The following display from a TI-84 Plus calculator presents a 95% confidence interval for the difference between two means. The sample sizes are $n _ { 1 } = 8 \text { and } n _ { 2 } = 13$ $\text { Compute the point estimate of } \mu _ { 1 } - \mu _ { 2 } \text {. }$
A) 123.288
B) 40.864
C) 42.032
D) -1.557

Question

The following display from a TI-84 Plus calculator presents a 95% confidence interval for the difference between two means. The sample sizes are $n _ { 1 } = 8 \text { and } n _ { 2 } = 13$ $\text { Compute the point estimate of } \mu _ { 1 } - \mu _ { 2 } \text {. }$
A) 123.288 
B) 40.864 
C) 42.032 
D) -1.557

Quizplus · Accepted Answer

The point estimate of $\mu _1 - \mu _2$ would be the midpoint of the confidence interval, which is given by $\text{mean}_1 - \text{mean}_2$. However, we are not given the sample means. Instead, we are given the interval estimate: (36.768, 47.296). The midpoint of this interval is (36.768 + 47.296)/2 = 42.032. Therefore, the best choice is C.

The Following Display from a TI-84 Plus Calculator Presents a 95