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...

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=32.7σ=32.7 dollars. You would like to be 90% confident that your estimate is within 2.5 dollar(s) of average spending on the birthday parties. How many parents do you have to sample?

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