91影视

Who talks more鈥攚omen or men? According to Louann Brazening, author of The Female Brain,

women say nearly three times as many words per day as men. Skeptical researchers devised a study to test this claim. They used electronic devices to record the talking patterns of $396$ university students who volunteered to participate in the study. The device was programmed to record $30$ seconds of sound every $12.5$ minutes without the carrier鈥檚 knowledge. According to a published report of the study in Scientific American, 鈥淢en showed a slightly wider variability in words uttered... But in the end, the sexes came out just about even in the daily averages: women at $16,215$ words and men at $15,669.鈥�56$ This difference was not statistically significant. What conclusion can we draw from this study? Explain.

Attend church, live longer? One of the better studies of the effect of regular attendance at religious

services gathered data from a random sample of $3617$ adults. The researchers then measured lots of variables, not just the explanatory variable (religious activities) and the response variable (length of life). A news article said: 鈥淐hurchgoers were more likely to be nonsmokers, physically active, and at their right weight. But even after health behaviors were taken into account, those not attending religious services regularly still were about $25\%$ more likely to have died.鈥�$57$ What conclusion can we draw from this study? Explain.

Daytime running lights Canada requires that cars be equipped with 鈥渄aytime running lights,鈥�

headlights that automatically come on at a low level when the car is started. Some manufacturers are now equipping cars sold in the United States with running lights. Will running lights reduce

accidents by making cars more visible? An experiment conducted in a driving simulator suggests that the answer may be 鈥淵es.鈥� What concerns would you have about generalizing the results of such an experiment?

Studying frustration A psychologist wants to study the effects of failure and frustration on the

relationships among members of a work team. She forms a team of students, brings them to the

psychology lab, and has them play a game that requires teamwork. The game is rigged so that they lose regularly. The psychologist observes the students through a one-way window and notes the changes in their behavior during an evening of game playing. Can the psychologist generalize the results of her study to a team of employees that spends months developing a new product that never works right and is finally abandoned by their company? Explain.

Minimal risk? You have been invited to serve on a college鈥檚 institutional review board. You must

decide whether several research proposals qualify for lighter review because they involve only minimal risk to subjects. Federal regulations say that 鈥渕inimal risk鈥� means the risks are no greater than 鈥渢hose ordinarily encountered in daily life or during the performance of routine physical or psychological examinations or tests.鈥� That鈥檚 vague. Which of these do you think qualifies as 鈥渕inimal risk鈥�?

(a) Draw a drop of blood by pricking a finger to measure blood sugar.

(b) Draw blood from the arm for a full set of blood tests.

(c) Insert a tube that remains in the arm, so that blood can be drawn regularly.

A farmer brings a juice company several crates of oranges each week. A company inspector looks at $10$ oranges from the top of each crate before deciding whether to buy all the oranges.

Does reducing screen brightness increase battery life in laptop computers? To find out, researchers obtained $30$new laptops of the same brand. They chose $15$of the computers at random and adjusted their screens to the brightest setting. The other $15$laptop screens were left at the default setting鈥攎oderate brightness. Researchers then measured how long each machine鈥檚 battery lasted.

Was this an observational study or an experiment? Justify your answer.

Do you trust the Internet? You want to ask a sample of high school students the question 鈥淗ow much do you trust information about health that you find on the Internet鈥攁 great deal, somewhat, not much, or not at all?鈥� You try out this and other questions on a pilot group of $5$ students chosen from your class. The class members are listed at the top right.

(a) Explain how you would use a line of Table D to choose an SRS of $5$ students from the following list. Explain your method clearly enough for a classmate to obtain your results.

(b) Use line $107$ to select the sample. Show how you use each of the digits.

Who reviews? Government regulations require that institutional review boards consist of at least five people, including at least one scientist, one nonscientist, and one person from outside the institution. Most boards are larger, but many contain just one outsider.

(a) Why should review boards contain people who are not scientists?

(b) Do you think that one outside member is enough? How would you choose that member? (For example, would you prefer a medical doctor? A member of the clergy? An activist for patients鈥� rights?)

No consent needed? In which of the circumstances below would you allow collecting personal

information without the subjects鈥� consent?

(a) A government agency takes a random sample of income tax returns to obtain information on the average income of people in different occupations. Only the incomes and occupations are recorded from the returns, not the names.

(b) A social psychologist attends public meetings of a religious group to study the behavior patterns of members.

(c) A social psychologist pretends to be converted to membership in a religious group and attends private meetings to study the behavior patterns of members.