Question 3: Statistical Inference 15. The mean service time at the McDonalds in Kennedy Town is 3 minutes. Assume the service time follows an exponential distribution. The standard deviation of the population is 3 minutes. You observe service times for a random sample of 49 customers at the McDonalds. What is the probability that the sample mean is more than 4 minutes? 16. A procurement manager at Best Buy wants to find out the population mean monthly sales of 4K TV at stores in the Midwest. Best Buy's current inventory policy is set under the assumption that 25 4K TVs are sold in a month on average. A sample of 49 stores was selected, and it was found that the sample mean is 19 with a sample standard deviation of 7. Does the sample data suggest that Best Buy needs to revise its inventory policy? Test at the a = .05 significance level.

Suppose that the walking step lengths of adult males are normally distributed with a mean of 2.5 feet and a standard deviation of 0.2 feet. A sample of 41 men’s step lengths is taken.   Step 2 of 2 :   Find the probability that the mean of the sample taken is less than 2.2 feet. Round your answer to 4 decimal places, if necessary.

Suppose that the walking step lengths of adult males are normally distributed with a mean of 2.7 feet and a standard deviation of 0.3 feet. A sample of 70 men’s step lengths is taken.   Step 2 of 2 :   Find the probability that the mean of the sample taken is less than 2.4 feet. Round your answer to 4 decimal places, if necessary.

A population has a mean µ = 87 and a standard deviation o=27. Find the mean and standard deviation of a sampling distribution of sample means with sample size n = 81. (Simplify your answer.)

7a. Suppose you go to Alaska in February where the chance of snow is .90 (90 percent).  You are there for two days.  Make the probability distribution associated with this experience. b. Find the mean, variance, and standard deviation for number 7.

A psychologist has designed a questionnaire to measure individuals' aggressiveness. Suppose that the scores on the questionnaire are normally distributed with a standard deviation of 80. Suppose also that exactly 15% of the scores exceed 750. Find the mean of the distribution of scores. Carry your intermediate computations to at least four decimal places. Round your answer to at least one decimal place.

A mechanic sells a brand of automobile tire that has a life expectancy that is normally distributed, with a mean life of 34,000 miles and a standard deviation of 2200 miles. He wants to give a guarantee for free replacement of tires that don't wear well. How should he word his guarantee if he is willing to replace approximately 10% of the tires? Click to view page 1 of the table. Click to view page 2 of the table. ****... Tires that wear out by miles will be replaced free of charge. (Round to the nearest mile as needed.)