EBook Problems EDA Statistics

EBook Problems Set - Statistics Problems

Problem 1

A recent Gallup Poll found that 23% of senior citizens exercise at least 3 times a week. The number 23% is:

• Choose one answer.

(a) A sample

(b) An estimate of the percentage of all senior citizens who exercise in the population

(c) The percentage of all senior citizens who exercise in the population

(d) A parameter

Problem 2

A student said his SAT Math score was at the 90th percentile. This means that:

• Choose one answer.

(a) The student got 90% of the questions wrong

(b) 90% of the class had a lower score than the student

(c) The student got 90% of the questions right

(d) 90% of the class had a higher score than the student

Problem 3

A random sample of 1000 US adults were interviewed and it was found that 2 of them had a rare disease known as diseaseA. Which of the following is true?

• Choose one answer.

(a) The standard error of the sample proportion is 5%

(b) 1000 is not a large enough sample to be able to construct a 99.7% confidence interval

(c) There is no way we can figure out whether the sample is too large or too small to construct an interval

(d) 2% of people in the sample have diseaseA

Problem 4

The Caldwells want to buy a new car, and they have narrowed their choices to a Buick or an Oldsmobile. They first consulted an issue of Consumer Reports, which compared rates of repairs for various cars. Records of repairs done on 400 cars of each type showed somewhat fewer mechanical problems with the Buick than with the Oldsmobile. The Caldwells then talked to three friends, two Oldsmobile owners and one former Buick owner. Both Oldsmobile owners reported having a few mechanical problems, but nothing major. The Buick owner, however, exploded when asked how he liked his car: first, the fuel injection went out, which cost $250 to fix. Next, he started having trouble with the rear end and had to replace it. He finally decided to sell it after the transmission went. He says he'd never buy another Buick. The Caldwells want to buy the car that is less likely to require repairs. Given what they currently know, which car would you recommend that they buy?

• Choose one answer.

(a) I would recommend that they buy the Buick despite their friend's bad experience. He is just one case, while the information reported in Consumer Reports is based on many cases. According to that data, the Buick is somewhat less likely to require repair.

(b) I would recommend that they buy the Oldsmobile, primarily because of all the trouble their friend had with his Buick. Since they haven't heard similar horror stories about the Oldsmobile, they should go with it.

(c) I would tell them that it does not matter which car they bought. Even though one of the models might be more likely than the other to require repairs, they could still, just by chance, get stuck with a particular car that would need a lot of repairs.

Problem 5

5. Used cars like yours are selling for a mean price $25,000 with a standard deviation of $1,000. You plan to sell your car so that you can buy a boat in Europe. The average cost of a boat in Europe is 20,000 Euros with a standard deviation of 600 Euros. What can you expect in your pocket after the sale and subsequent purchase? One US dollar is 0.9 Euros.

• Choose one answer.

(a) -$2,500

(b) $5,000

(c) $2,500

(d) $10,000

Problem 6

In either a survey situation or a manufacturing process, what can we do to offset a large population standard deviation to still obtain accuracy of our sample mean?

• Choose one answer.

(a) Select a smaller sample size

(b) Give up! There is nothing you can do in this case

(c) Select a larger sample size

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• SOCR Home page: http://www.socr.ucla.edu

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