Bob Nale is the owner of Nale’s Quick Fill. Bob would like to estimate the mean

Question

Bob Nale is the owner of Nale’s Quick Fill. Bob would like to estimate the mean number of gallons of gasoline sold to his customers. Assume the number of gallons sold follows the normal distribution with a population standard deviation of 1.90 gallons. From his records, he selects a random sample of 75 sales and finds the mean number of gallons sold is 5.40. a. What is the point estimate of the population mean?(Round your answer to 2 decimal places.)

Point estimate b. Determine a 99% confidence interval for the population mean. (Use z Distribution Table.) (Round your answers to 2 decimal places.) Confidence interval and .

Explanation / Answer

Mean is 5.4 and s is 1.9. sample size is 75. thus standard error is 1.9/sqrt(75)=0.2194

a) Mean is same as 5.4

b) for 99% confidence, the z value is 2.575

thus lower limit is mean-SE*z =5.4-0.2194*2.575=4.835

and upper limit is mean+SE*z =5.4+0.2194*2.575 =5.965

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