The Professor's Response

Hello Professor disregard the question I just asked " in the homework section 9.8 problem 35 I am not getting the right numbers for the interval. My critical value is 3.106 and the test stat comes out to be 3.16. What am I doing wrong?" my critical value was incorrect now I have the interval [-3.24, 1.24].

See the professor's answer below.

Hi Sheyla,

When I subtract the two rows of data (Reported - Measured), I get an average difference of -1.0.

The data for this problem is then:

n = 12

X-bar = -1.0

S = 3.5196

CL = 0.95

The critical ta/2, df value is: t0.025, 11 = 2.201

This gives us a margin of error of: E = 2.201*3.5196/root(12) = 2.2363.

The final interval is (-1.0 - 2.2363, -1.0 + 2.2363) = (-3.2363, 1.2363).

**note: if I had done my subtraction in the other order, I would have the answer: (-1.2363, 3.2363).

I hope this answers your question,

Professor McGuckian