A researcher wishes to estimate, with 90% confidence, the population proportion

Question

A researcher wishes to estimate, with 90% confidence, the population proportion of adults who are confident with their country's banking system. His estimate must be accurate within 5% of the population proportion.

(a) No preliminary estimate is available. Find the minimum sample size needed.

(b) Find the minimum sample size needed, using a prior study that found that 26% of the respondents said they are confident with their country's banking system.

(c) Compare the results from parts (a) and (b).

Explanation / Answer

a) for no preliminary estimate we copnsider p=0.5

margin of error =0.05

and for 90% CI, z=1.64485

hence sample size =(p1(-p))(Z/E)2 =~271

b)for p=0.26

sample size =~209

c) as estimation not available ; sample size in part a is greater.

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