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13) Confidence Interval Sample Size You must show your work for full credit. To show your work; 1. Write the formula that relates the sample size with the margin of error and confidence level 2. Correctly enter the values in the correct spots 3. correctly round to the correct whole number. 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 o = 72.1 dollars. You would like to be 95% 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? n=