Aresearcher wishes to estimate, with 9090% confidence, the proportion of adults who have high-speed internet access. her estimate must be accurate within 55% of the true proportion. a) find the minimum sample size needed, using a prior study that found that 2828% of the respondents said they have high-speed internet access. b) no preliminary estimate is available. find the minimum sample size needed.

 a) Required minimum sample size= 219

b) Required minimum sample size= 271

Step-by-step explanation:

As per given , we have

Margin of error : E= 5% =0.05

Critical z-value for 90% confidence interval :

a) Prior estimate of true proportion: p=28%=0.28

Formula to find the sample size :-

Required minimum sample size= 219

b) If no estimate of true proportion is given , then we assume p= 0.5

Formula to find the sample size :-

Required minimum sample size= 271

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step-by-step explanation: