The Highway Safety Department wants to study the driving habits of individuals. A sample of 38 cars traveling on a particular stretch of highway revealed an average speed of 67 miles per hour with a standard deviation of 3.8 miles per hour. Round to 4 decimal places. 1.Calculate a 90% confidence interval for the true mean speed of all cars on this particular stretch of highway. 2. What sample size is needed to estimate the true average speed to within 0.5 mph at 90% confidence? Note: For consistency's sake, round your t* value to 3 decimal places before calculating the necessary sample size. Choose n =
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Step 2: Calculate the necessary sample size to estimate the true average speed to within 0.5 mph at a 90% confidence level. **Step 1:** Given data: Sample mean (X bar) = 67 mph Sample standard deviation (s) = 3.8 mph Sample size (n) = 38 Confidence level = 90% Show more…
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