A sample of 100 randomly selected customers shopped in a certain hardware store

Question

A sample of 100 randomly selected customers shopped in a certain hardware store for an average of 19 minutes. Assume the population standard deviation = sigma = 5.5 minutes. What can the store manager say about the average shopping time of customers with confidence? Interpret your answer. A random sample of 26 students has an average grade of 78.5. Suppose the population standard deviation is 19.2. Construct a 97% confidence interval of the average of all students. Ms. Tran has to commute to work every day and she wants to know how many minutes she must spend each day driving to/from work. Here is the collection of minutes of 10 randomly selected days in March. 58, 46, 64, 42, 49, 53, 57, 65, 52, 55 Assume the population standard deviation = sigma = 12 minutes. Construct a 95% confidence in of the average number of minutes of her commute. Suppose a random sample of 10 students with Exam #2 grades: 44, 59, 87, 68, 89, 90, 77, 91, 96, 65 Assume the population standard deviation = sigma = 21. Is there enough evidence to suggest average that the average of Exam #2 is below 85? A sample of 20 students with average of 7.04 hours of sleep per night. Assume the population standard deviation = sigma = 1.2 hours. Is there enough evidence to claim that on average students get less than 8 hours of sleep per night at alpha = 10%? At alpha = 1%? A sample of 90 girls with an average height of 5.4 feet. Assume the population is normal with standard deviation of 0.6 foot. Is there enough evidence to claim that the average of all girls is less than 5.6 feet at the 1% level?

Explanation / Answer

1.

n = 100

mean = 19min

sigma = 5.5min

A 99% Confidene is 19 +/- 2.575*5.5/sqrt(100) = 17.58 to 20.42

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