Question 1182994: You want to obtain a sample to estimate how much parents spend on their kids birthday parties. Based on previous study, you believe the population standard deviation is approximately
σ
=
71.7
σ
=
71.7
dollars. You would like to be 99% confident that your estimate is within 4 dollar(s) of average spending on the birthday parties. How many moms do you have to sample? Do not round mid-calculation.
n =
Try this with your statistics calculator, if you decreases the confidence level, the sample size
increases
decreases
If you decreases the error bound, the sample size
decreases
increases
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! error=z*sigma/sqrt(n), square both sides
4^2=2.576^2*71.7/(n)
multiply by n and divide by 16
do without rounding the z-value
n=2131.82 or 2132
-
decrease confidence, sample size gets smaller
decrease the error, sample size gets larger
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