A reporter wishesto estimate the percent of men at a rally. In a random sampleof

Question

A reporter wishesto estimate the percent of men at a rally. In a random sampleof 1357 people at the rally, he observed 246 men.

Is 246 the EXPECTED orOBSERVED value for the number of men in the sample?

i answered observed. am icorrect? if no, why?

Is the SD of the boxEXACTLY EQUAL TO or ESTIMATED FROM THE DATA as the square root of0.181*0.819?

i answered estimated fromthe data. am i correct? if no, why?

Find a 95%-confidenceinterval for the percentage of men at the rally? (assume that thesample is sufficiently large hat a normal approximation isapplicable)

i do not know how to dothis. could someone please show me how?

Explanation / Answer

For the first 2 question, your own answer is correct. :) 95% confidence interval = ps ± Z/2(pq/n)      where ps =0.181 and = 0.05 = 0.181 ± 1.96*(0.181*0.819/1357) = 0.181 ± 0.020 =(0.161,0.201)

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