Chapter 1Do Not Write on This Paper

CHAPTER 1DO NOT WRITE ON THIS PAPER!!!

1.In one of the first attempts to discover the speed of light, Simon Newcomb in 1882 made 92 measurements of the time

light takes to travel between the Washington Monument and his laboratory on the Potomac River. Why did

Newcomb repeat his measurement 92 times and the take the average of the 92 as his final result?

(a) Averaging several measurements reduces any bias that is present in his instruments.

(b) The average of several measurements is more reliable (less variable) than a single measurement.

(d) Both (a) and (b) but not (c).

(e) All of (a), (b), and (c).

2. Professor Iconu has developed a new college entrance test. Any such test must have several versions because some

people take the test more than once. Unfortunately, it turns out that the same person often gets very different scores

depending on which version of the test is offered. The test suffers from

(a) large bias. (b) confounding. (c) low accuracy. (d) low reliability.

3. During a visit to the doctor, you are weighed on a very accurate scale. You are weighed five times and the five readings

are essentially the same. When being weighed, you are wearing all of your clothes AND a solid gold chain necklace

(it is very heavy). As a measure of your weight without clothes, the reading on the scale is

(a) unbiased and reliable

(b) unbiased and unreliable

(d) biased and unreliable

(e) biased and reliable

4. An ad for a new mouth rinse says that it "reduces plaque on teeth by 300 percent." What does this mean?

(a) It means that three-tenths of the plaque is removed, because 300/1000 = 0.3, or three-tenths.

(b) It's nonsense, because plaque is a categorical variable, so percents don't make sense.

(d) It's nonsense, because removing 100 percent of the plaque already removes all of it.

(e) It's nonsense because percents only make sense for counts, and amount of plaque isn't a count.

5. You measure the age (years), weight (pounds), and marital status (single, married, divorced, or widowed) of 1400

women. How many variables did you measure?

(a) 1400 (b) one (c) two (d) three (e) 1403

6. Following are data on the populations and numbers of death row prisoners for several states.

STATE POPULATION DEATH ROW PRISONERS

California28,168247

Florida12,377294

Illinois11,544120

Nevada1,06045

Which state has the lowest number of death row prisoners relative to the size of its population?

(a) California (b) Florida (c) Illinois (d) Nevada

7. The Dow Jones Industrial Average (DJIA) is the most common measure of stock market prices. Suppose that the DJIA

starts at 9000 points and drops 300 points. This is a decrease of

(a) 0.033% (b) 3.3% (c) 33.3% (d) 333%

8. A 300 point drop in the DJIA was a big drop when the DJIA was at 2000 and a much smaller drop when the DJIA

reached 9000. The percent by which stock prices fall is a more meaningful measure. The lesson here is that

(a) rates are often more meaningful than counts

(b) it is easy to make a mistake calculating a percent

(d) there are lies, damned lies, and statistics.

9. Amy wants to spend a summer in France after she graduates. She is worried that this will be too expensive because the

dollar buys fewer French francs now. When Amy entered college, a dollar was worth 6.5 francs. Now a dollar is worth

only 5.25 francs. By about what percent has the value of the dollar in francs decreased?

(a) 10% (b) 19%(c) 24% (d) 76% (e) 81%

10. A researcher creates a machine that will measure the total electrical activity in a human brain over a short period of

time. She claims that this measures the intelligence of the brain's owner. A psychologist says that's not true because

the amount of electrical activity isn't related to ability to solve problems. The psychologist is claiming that electrical

activity as a measure of intelligence is

(a) invalid. (b) biased. (c) not reliable. (d) not accurate.

11. A dishonest butcher has a scale on which he weighs the meat his customers buy. In order to increase his profits, he has

doctored the scale so that it always reads very close to 10 percent more than the actual weight. The measurements

from this scale are

(a) biased and unreliable

(b) biased and reliable

(d) unbiased and reliable

Free response:

1.A clothing designer is cutting strips of fringe to embellish a skirt. She wants the strips to be 8 cm long. Using her ruler,

she measures as follows:

The designer’s intern comes in and points out that the designer has been incorrectly measuring from the very edge of the ruler. Is this mistake due to lack of validity, lack of reliability, or bias? Explain.

2. A pollster asks 1000 high school students who their favorite baseball team is. Over half say, “The Giants, duh!”. In this

situation, identify the population, the sample, the individuals, and the variable. Is this an example of an experiment,

census, sample survey, or observational study?

3. Describe the difference between a census (with a lowercase “c”) and the Census (with an uppercase “C”).

4. You are explaining to your friends why the senior class is the best. You make the argument that 385 of the seniors

dressed up during spirit week. A silly freshman replies that 401 of the freshmen dressed up, so the Freshman class

obviously has more school spirit. Explain to him why the senior class (with 417 members total) is CLEARLY superior

to the Freshman class (with 648 members total).

5. For a statistics project, you and a partner decide to survey seniors to determine whether they are planning on attending

the senior trip to Disneyland. You ask 20 seniors. Your partner types the report, which includes the following:

“After surveying 20 seniors, we found that 73% of seniors are planning on attending the trip”.

Explain to your partner why you are questioning their results.