The Professor's Response

Hi Prof i was wondering if you could help me with number 38 from chapter nine in the homework.

I keep trying and trying and i keep getting the wrong answer and i don't know what I'm doing.
I have

N: 60
p hat: i divided 52/60: .8667
and q hat is 1-.8667 and i got .133

N: 58
p hat: 56/58 and got .9655
q hat: 1-.9655

i don't know if thats the right data but i keep getting the wrong answer

  See the professor's answer below.

Professor McGukian

Hi Sandra,

Here is what you need to do for this problem:

The data you listed is correct.

The confidence level is 90%, so the alpha is 10%. This means Za/2 = Z0.05 = 1.645.

Then the margin of error is then, E = 1.645*SqrRoot(0.8667*0.1333/60 + 0.9655*0.0345/58) = 0.0822

Finally, (pm - pw - E, pm - pw + E) = (-0.0988 - 0.0822, -0.0988 + 0.0822) = -0.181 to -0.017. 

*If you round to whole percents, -18% to -2%.

Hope that helps you find your error,

Professor McGuckian


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