Question

In a election, we want to estimate the proportion of the voters for X party assuming initially that =0.5 with a 90% confidence, within an error of 2%.

(a) How many voters should we polled for that? the sample size is . Show your steps on a separate paper

(b) If the number of voters for X party are eventually 2000, with 800 voters for X give the corresponding confidence interval?

Lower limit is

Upper Limit is

Answer 1

(a)given data are:-

sample proportion () = 0.5

margin of error (E) = 2% = 0.02

z critical value for 90% confidence level, both tailed test be:-

the number of voters should we polled for that is :-

(b) sample proportion () = 800/2000 = 0.4

the 90% confidence interval be:-

Lower limit is = 0.382

Upper Limit is = 0.418

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