7.20. A district sales manager for a franchise fast-food company want to determine the average sales of a burger that they recently introduced. In a random sample of 30 locations, the average daily sales was found to be $5420 with a standard deviation of $510. a. Calculate the margin of error for a 90% confidence interval for the average sales of the burger that they recently introduced. b. Construct the 90% confidence interval for the average sales of the burger that they recently introduced. c. Interpret the interval in part b. cl. How large of a sample size is necessary to reduce the 90% margin of error to $120? Confidence Intervals for p Construct a 95% confidence interval to estimate the proportion of all taxpayers who filed electronically in 2018. 0.9333 10.9333 09333 i 1.96 - 1/ % 0.9333 :l: 1.96 . 0.0166 0.9333 i 0.0325 (0.9008, 0.9658) Determining Sample Size for p Let's explore the affect on the sample size by changing the critical value using the IRS dataset: f3 = 0.9333, MoE = 0.05. o 90% confidence level n : 1.6452-0903391093331 : 67.381 T 68 o 95% confidence level n : 1.962-0.9303"35!10.3933! : 95658 T 96 o 99% confidence level n : 2.582-0.9%935!10.9333! : 165.747 T 166