Mathematics

Question 11 of 20 1.0 Points

A researcher wishes to know, with 98% confidence, the percentage of women who wear shoes that are too small for their feet. A previous study conducted by the Academy of Orthopedic Surgeons found that 80% of women wear shoes that are too small for their feet. If the researcher wants her estimate to be within 3% of the true proportion, how large a sample is necessary?

 

[removed] A.966
[removed] B.683
[removed] C.183
[removed] D.484
Question 12 of 20 1.0 Points

A recent study of 750 Internet users in Europe found that 35% of Internet users were women. What is the 95% confidence interval estimate for the true proportion of women in Europe who use the Internet?

 

[removed] A.0.321 < p < 0.379
[removed] B.0.316 < p < 0.384
[removed] C.0.309 < p < 0.391
[removed] D.0.305 < p < 0.395
Question 13 of 20 1.0 Points

At a large department store, the average number of years of employment for a cashier is 5.7 with a standard deviation of 1.8 years. If the number of years of employment at this department store is normally distributed, what is the probability that a cashier selected at random has worked at the store for over 10 years?

 

[removed] A.0.4916
[removed] B.0.9916
[removed] C.0.0084
[removed] D.0.0054
Question 14 of 20 1.0 Points

A previous study of nickels showed that the standard deviation of the weight of nickels is 150 milligrams. How many nickels does a coin counter manufacturer need to weigh so that she can be 98% confident that her sample mean is within 25 milligrams of the true average weight of a nickel?

 

[removed] A.36
[removed] B.196
[removed] C.239
[removed] D.139
Question 15 of 20 1.0 Points

If you increase the confidence level, the confidence interval ____________.

 

[removed] A.decreases
[removed] B.may increase or decrease, depending on the sample data
[removed] C.increases
[removed] D.stays the same
Question 16 of 20 1.0 Points

Compute P( t20 _< – 0.95)   where t20 has a t-distribution with 20 degrees of freedom.

 

[removed] A.0.5334
[removed] B.0.1767
[removed] C.0.8233
[removed] D.0.6466
Question 17 of 20 1.0 Points

In a study of elephants a researcher wishes to determine the average weight of a certain subspecies of elephants. From previous studies, the standard deviation of the weights of elephants in this subspecies is known to be 1500 pounds. How many elephants does the researcher need to weigh so that he can be 80% confident that the average weight of elephants in his sample is within 350 pounds of the true average weight for this subspecies?

 

[removed] A.166
[removed] B.31
[removed] C.50
[removed] D.39
Question 18 of 20 1.0 Points

In order to be accepted into a top university, applicants must score within the top 5% on the SAT exam. Given that SAT test scores are normally distributed with a mean of 1000 and a standard deviation of 200, what is the lowest possible score a student needs to qualify for acceptance into the university?

 

[removed] A.1330
[removed] B.1400
[removed] C.1250
[removed] D.1100
Part 3 of 3 –

 

Question 19 of 20 1.0 Points

A 90% confidence interval estimate for a population mean is determined to be 72.8 to 79.6. If the confidence level is reduced to 80%, the confidence interval becomes narrower.

 

[removed] True
[removed] False
Question 20 of 20 1.0 Points

In general, increasing the confidence level will narrow the confidence interval, and decreasing the confidence level widens the interval.

 

[removed] True
[removed] False

 

 

 

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