In a poll to estimate presidential popularity, each person in a random sample of

Question

In a poll to estimate presidential popularity, each person in a random sample of 1,190 voters was asked to agree with one of the following statements:

A total of 650 respondents selected the first statement, indicating they thought the president was doing a good job.

Construct a 99% confidence interval for the proportion of respondents who feel the president is doing a good job. (Use z Distribution Table.) (Round your answers to 3 decimal places.)

Based on your interval in part (a), is it reasonable to conclude that a majority of the population believes the president is doing a good job?

Explanation / Answer

a)

Note that              
              
p^ = point estimate of the population proportion = x / n =    0.546218487          
              
Also, we get the standard error of p, sp:              
              
sp = sqrt[p^ (1 - p^) / n] =    0.014432219          
              
Now, for the critical z,              
alpha/2 =   0.005          
Thus, z(alpha/2) =    2.575829304          
Thus,              
              
lower bound = p^ - z(alpha/2) * sp =   0.509043554          
upper bound = p^ + z(alpha/2) * sp =    0.583393421          
              
Thus, the confidence interval is              
              
(   0.509043554   ,   0.583393421   ) [ANSWER]

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b)

Yes, because the whole interval is totally greater than 0.50. [ANSWER]

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