Statistics 1 Quiz

1.

You are buying uniforms for young male military recruits. You know the mean chest size and the standard deviation of the chest size. About what proportion of the chest sizes of the recruits would you expect to be within one standard deviation of the mean chest size? Choose the best answer.

a. 50%, if the mean chest size is Normally distributed

b. 2/3

c. 50%, if the chest sizes are Normally distributed

d. 68%, if the chest sizes are Normally distributed

e. 95%

2.

This question is about a drug study to compare two treatments for reducing blood pressure. A suitable group of patients is recruited and randomly divided into two groups, each group receiving one of the drugs. At the end of the study period, you make the graphs of the reduction in blood pressure. The y-axis shows a reduction in blood pressure. Based on the graph, which group had the greatest reduction in blood pressure?

a. Group 0

b. Group 1

c. Too close to call

d. Not enough information to tell

3.

Continuing with the blood pressure study, and based on the graph, which group has the greater variability?

a. About the same

b. Group 0 is much more variable

c. Group 1 is much more variable

d. Not enough information to tell

4.

You are studying economic development in a small developing country. You do not have individual income data but you do have counts of how many people fall into various intervals such as 0-500, 501-1000, etc. You want a display that shows the shape of the income distribution. You should make a

a. Scatter plot

b. Pie chart

c. Bar chart

d. Histogram

5.

The plot above shows the monthly incomes of a sample of households in 2011 in Poland (from "Environmental and Resource Economics", 2020, v. 76). Which is more likely?

a. The mean is smaller than the median

b. The mean is larger than the median

c. The mean is equal to the median

d. We cannot say without having the actual numbers

6.

You have data on the number of graduates in engineering from a sample of eight colleges that grant engineering degrees. You wish to make a graphical display to compare the number of engineers produced by these eight schools. A good choice would be

a. Scatter Plot

b. Histogram

c. Pie chart

d. Bar chart

7.

Your study produced 27 weights in kilograms which you need to analyze. Which of the following statistics will NOT have units of kilograms?

a. Mean

b. Median

c. Variance

d. Standard deviation

8.

You wish to know whether adding vinegar as an ingredient in making bread will retard the growth of mold on the bread. You can best answer this question with

An observational study

An experiment

A survey

Any of the above would be equally good

9.

Suppose a website gets 5000 visitors in a week, and 100 of them click on a product link. Of the ones who click on the product link, 8 purchase the product. What is the (a) unconditional (simple) probability of a visitor making a purchase, and (b) the probability of a visitor making a purchase, conditional on clicking on the product link?

a. a=0.0016 b=0.02

b. a=.02, b=0.08

c. a=0.0016, b=0.08

d. a=0.50, b=0.08

10.

An analyst examining the analytics for her company's website reports that the probability is 0.07 that a visitor will view the page concerning a newsletter subscription, and 0.04 that a visitor will view the page concerning the company's security monitoring product. What is the probability that a visitor will visit either one page or the other?

a. 0.028

b. 0.28

c. 0.11

d. Cannot determine without knowing whether the events are independent.

11.

After seismic studies at a particular site, geologists figure that an oil well has a 60% chance of producing 100 barrels a day, a 30% chance of producing 30 barrels a day, and a 10% chance of producing nothing. What is the expected value of the well, in terms of barrels per day?

a. 69 barrels/day

b. 100 barrels/day

c. 60 barrels/day

d. Cannot determine without knowing whether the outcomes are independent.

12.

A transportation consultant is reviewing airline customer data as part of an effort to improve the algorithm that determines whether a passenger gets pulled aside for further screening. Various metrics are reviewed and the data are standardized (normalized) so as to be comparable to one another. One metric is the value of the ticket. Suppose the mean ticket value is $324 and the standard deviation is $156. What would the normalized value be for a fare of $585?

a. 1.67

b. 261

c. 429

d. 0.48

13.

Economists reviewing certain income data determine that it is not Normally-distributed, so they decide to standardize it and convert it to z-scores. As a result,

a. The z-scores are now Normally-distributed

b. The z-scores, and comparison to a Normal distribution, can be used to determine what portion of the population falls into various income brackets.

c. Both of the above

d. None of the above

14.

A polygraph (lie detector) has the following performance attributes: If someone is lying, there is a 70% probability the machine will catch them. If someone is not lying, there is a 25% chance the machine will erroneously flag them as lying. If someone takes the test and the machine says "lying", what is the approximate probability that the person is actually lying? Assume 85% of those taking the test are not lying.

a. 1/3

b. 0.75

c. 0.70

d. 0.60

15.

The marketing department at a mobile device manufacturer wants to gauge whether consumers would favor a device with larger dimensions. A proposal from a market research firm calls for surveying 1000 consumers, identifying sources of names and criteria for random selection, and contacting them by telephone, if needed for a response. The marketing manager points out that a much larger survey could be conducted much more cheaply simply using a popup on existing customer devices. Which of the following is true?

a. The smaller sample is likely to have less bias than the popup survey, but the greater size of the popup survey will correct for this effect.

b. A much more accurate answer could be obtained with the larger sample, but only if it exceeds 1000 by at least one standard deviation.

c. The smaller sample is likely to be more accurate, since it is more likely to avoid bias.

d. The smaller sample is likely to be more accurate, due to the higher standard deviation for the data it is measuring.

16.

A newspaper is worried about declining subscriptions and finds that it does not have good information about how many people are canceling. It randomly selects 100 current subscribers for closer study and finds that 5 of them had canceled at the end of one month. So the estimated cancellation rate is 5% per month. Which of the following procedures might be used in establishing possible sampling error in this 5% estimate?

a. Place 20 slips of paper in a box, 1 marked “cancel” and 19 marked “don’t cancel,” randomly draw 100 with replacement.

b. Place 100 slips of paper in a box, 5 marked “cancel” and 95 marked “don’t cancel,” randomly draw 9 with replacement.

c. Place 100 slips of paper in a box, 9 marked “cancel” and 91 marked “don’t cancel,” randomly draw 9 with replacement.

d. Place 91 slips of paper in a box, 9 marked “cancel” and the rest marked “don’t cancel,” randomly draw 100 with replacement.

17.

A politician running for office after a scandal wants to learn his favorability ratings. He can afford a sample survey of 200 voters, from which he would calculate x = "number in the survey who regard him favorably" which would then be converted to a "percent favorable" estimate. Which of the following might be used after the survey to assess how much uncertainty there is in the resulting estimate, due to random chance?

a. A box with 100 slips of paper, x of them marked “favorable” and the remainder “not favorable”

b. A box with x slips of paper marked “favorable” and 200-x marked “not favorable.”

c. Random draws of x slips of paper from a box

d. Random draws of 200-x slips of paper from a box

18.

A research firm has just completed an opinion survey using a sample of 250 voters in Menlo Park CA (pop. 33,000). Now they plan to do the same survey in Palo Alto CA (pop 66,000). How many voters should they sample in Palo Alto to achieve about the same degree of accuracy as in Menlo Park?

a. 250

b. 350

c. 500

d. 660

19.

Say you are considering taking a survey of your customers, and weighing the option of (1) a small, low-cost survey, and (2) a larger, higher-cost survey. Which of the following is an accurate statement:

a. The confidence interval for the larger survey will be broader than the one for the smaller survey

b. The confidence interval for the smaller survey will be shorter than the one for the larger survey.

c. The more expensive survey will yield a confidence interval showing less uncertainty about the true value.

d. A 90% confidence interval for the larger survey will be right more often than a 90% confidence interval for the smaller survey.

e. None of the above

20.

Consider the reviews that you read of products and services that you read online, say at Amazon or Yelp. Which of the following is true?

a. The review process is prone to self-selection bias.

b. The review process is an example of simple random sampling, and uncertainty can be quantified via a confidence interval.

c. The review process incorporates stratification in the sampling, which reduces bias.

d. All of the above

e. None of the above

21.

About you: Are you looking for a statistics course that offers academic credit?

Yes

22.

First Name

Last Name

Email(Required)