Quick Quiz - Statistics.com: Data Science, Analytics & Statistics Courses

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

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

A blog serving the music business is worried about declining subscriptions and finds that it does not have good information about how many people are canceling, and when. 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.

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

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

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

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

d. There may be bias in the selection of reviews, but this is overcome with a large sample size.

Suppose a web site 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= 0.02, b=0.08

c. a= 0.0016, b=0.08

d. a= 0.5, b= 0.08

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