SOLUTION: You read about a survey in a newspaper and find that 70% of the 250 people sampled prefer Candidate A. You are surprised by this survey because you thought that more like 50% of th

Question 1086022: You read about a survey in a newspaper and find that 70% of the 250 people sampled prefer Candidate A. You are surprised by this survey because you thought that more like 50% of the population preferred this candidate. Based on this sample, is 50% a possible population proportion? Compute the 95% confidence interval to be sure.
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
95%CI is mean +/-1.96*SE
mean is point estimate, here 0.70
SE is sqrt (p*(1-p))/n, or sqrt (.21/250)=0.0290
interval width is 0.0568, after multiplying by 1.96
CI is {0.643, 0.757)
No, 50% is not a possible proportion. It is not in the interval.

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