1. The television program Nightline once asked viewers whether the United Nations should continue to have its headquarters in the United States. Two phone numbers were given. Viewers were asked to call one telephone number to respond "Yes" and the other to respond "No". More than 186,000 callers responded and 67% said "No." This is an example of
A. voluntary response sampling.
B. a survey with little bias because a large SRS was used.
C. a survey with little bias since someone who called would know his or her opinion.
D. all of the above.
2. The distribution of actual weights of 8 oz. wedges of cheddar cheese produced at a dairy is Normal with mean 8.1 ounces and standard deviation 0.1 ounces.
Reference: Ref 11-5
If a sample of five of these cheese wedges is selected, the probability that their average weight is less than 8 oz is (Use Table A)
A. 0.0125.
B. 0.1853.
C. 0.4871.
D. 0.9873.
3. A random variable can be described as
A. a probability of an event.
B. a variable whose value is a numerical outcome of a random phenomenon.
C. the proportion of times an event occurs over a long run of repeated trials.
D. all of the above.
4. A researcher plans to conduct a test of hypotheses at the ? = 0.05 significance level. She designs her study to have a power of 0.80 at a particular alternative value of the parameter of interest.
The probability that the researcher will commit a Type I error is
A. 0.05.
B. 0.20.
C. 0.80.
D. equal to the P-value and cannot be determined until the data have been collected.
5. At a large midwestern college, 4% of the students are Hispanic. A random sample of 20 students from the college are selected. Let X denote the number of Hispanics among them.
The mean of X is
A. 0.4.
B. 0.8.
C. 1.2.
D. 1.6.
6. Can brainwaves be used to measure job aptitude? During the 1980s, a psychologist tried to use brainwave measurements to identify U.S. Navy recruits who are good at using a rifle (instead of simply watching them shoot). Several times each year, batches of data were analyzed. Each batch of data compared various brainwave measurements with rifle-shooting performance records for a group of recruits. The psychologist was looking for evidence of a relationship between brainwave measures and shooting skill. During 1990, he analyzed 34 of these batches. In 32 of those batches, there was no evidence of association, but the other two batches were statistically significant (at level of significance ? = .05) in demonstrating a relationship between brainwaves and shooting skill. Based on this, which of the following is true?
A. The psychologist should toss out the 32 batches of data that failed to demonstrate an association between brainwaves and shooting skill, and keep the two batches that do demonstrate an association. After all, the grant that funds such research and pays the psychologist's salary needs to be renewed.
B. There's little evidence of an association. After all, since we're testing each batch of data at the ? = .05 level of significance, by chance alone 1 in 20 batches would demonstrate an association even if there really isn't one. This explains the two "good" batches the psychologist observed.
C. The psychologist should just pick one of the data sets (at random) and base his analysis on that.
D. All of the above.
7. Spelling mistakes in a text are either "nonword errors" or "word errors." A nonword error produces a string of letters that is not a word, such as "the" typed as "teh." Word errors produce the wrong word, such as "loose" typed as "lose." Nonword errors make up 25% of all errors. A human proofreader will catch 90% of nonword errors and 70% of word errors.
Of all the errors that the proofreader catches, what part are nonword errors?
A. 0.125
B. 0.225
C. 0.300
D. 0.375