1.Time taken for oil change
It is known that the amount of time needed to change the oil ona car is normally distributed with a standard deviation of 5minutes. The manager of a service shop recorded the amount of time(in minutes) to complete a random sample of 10 oil changes. Theyare listed below. 11 10 16 15 18 12 25 20 18 24
a. The sample average is: _______minutes (up to 2 decimal points)
B.The sample standard deviation is:_______ minutes (up to 2 decimal points)
The following information applies to the next two questions:
Compute a 95% interval estimate of the population mean.
- Lower Confidence Level ___ Minute (up to 2 decimal points)
- Upper Confidence Level ___ Minutes (up to 2 decimalpoints)
- Based on your answer above, if you take your car to thisparticular shop, your car will be serviced between andminutes. You are % certain about this.
- Suppose that the manager feels that the range of values heobtained above are too wide to attract customers. What can he do toobtain a narrower range of values?
Use a 90% confidence interval
Take a random sample of 100 oil changes
Train his employees well so that the variability in time tochange oil reduces
All the above
None of the above
- A marketing researcher wants to estimate the mean amount spent($) on Amazon.com by Amazon Prime member shoppers. A random sampleof 100 Amazon Prime member shoppers who recently made a purchase onAmazon.com yielded a mean of $1,500 and a standard deviation of$200.
Construct a 90% Confidence Interval estimate for the meanspending for all Amazon Prime shoppers.
What is the Lower Confidence Level $______
What is the Upper Confidence Level $______
8. Based on the above calculation, which one of the followingstatements is correct
We are 90% confident that an Amazon Prime Member spends$1500
We are 90% confident that an Amazon Prime Member spends between$1467.10 and $1532.90
Both of the above statements are true
An Amazon Prime member spends between $1467.10 and $1532.90
- The researcher is not happy with the estimate, and she wantstighter interval, i.e., a smaller level of error. If she wants theestimate to be within ±$25 with 90% confidence, what sample sizedoes she need?
Sample size _____ (report the next whole number, 100.2 should bereported as 101)
- The salaries of graduates from the MBA program of a Big Tenschool are NOT normally distributed. In order to get a betterunderstanding of the range of salaries made by the graduates, themarketing director compiles a five-year record of salaries offeredto students at campus recruitment events. He randomly selectsgroups of 120 students graduating in Fall, Summer, and Spring forthe past five years (i.e., 15 groups, each with 120 students).
According to the Central LimitTheorem, the salaries within any of these 15 groups will bedistributed normally. True or False?
According to the Central LimitTheorem, the average salaries of these 15 groups will bedistributed normally. True or False
