SOLUTION: People were polled on how many books they read the previous year. How many subjects are needed to estimate the number of books read the previous year within one book with 90% ̴
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Question 1043427: People were polled on how many books they read the previous year. How many subjects are needed to estimate the number of books read the previous year within one book with 90% confidence? Initial survey results indicate that σ=11.5 books. Round to the nearest whole number as needed. Answer by Boreal(15235) (Show Source):
You can put this solution on YOUR website! If it were a normal distribution, not a t, z=+/-1.645
the standard error is sigma/sqrt(n)
so 1.645*11.5/sqrt(n)=1
1.645*11.5=sqrt(n), multiplying through.
18.9175=sqrt(n)
square both sides
n=357.87 or 358 people. That would be fine with a normal distribution.
