Statistics Practice

Which of the following statements is true? a. Nonresponse can cause bias in surveys because non-respondents may have different opinions than people who responded. b. Bias arising from undercoverage can be compensated for by increasing sample size. c. Stratified random sampling is often employed to reduce the impact of response bias. d. People's responses to survey questions tend not to be influenced by the age, race, or sex of the interviewer.

a. Nonresponse can cause bias in surveys because non-respondents may have different opinions than people who responded.

The highway department is testing two different types of paint for use in painting lines on newly constructed roads. The department uses 20 different road segments in the study, with each type of paint randomly assigned to 10 of the road segments. The response variable will be the amount that the paint fades in a 6-month period. What is the most important reason for this random assignment. a. Random assignment eliminates the effects of other variables such as traffic volume and sun exposure. b. Random assignment is a good way to create two groups of road segments that are roughly equivalent. c. Random assignment makes it possible to generalize about all road segments. d. Random assignment reduces the variation in the amount of fading. e. Random assignment prevents the placebo effect from ruining the results of the study,

b. Random assignment is a good way to create two groups of road segments that are roughly equivalent.

An airline has 10 daily flights from Philadelphia to Denver. To assess customer satisfaction, a random sample of 15 passengers from each flight on a single day is asked to fill out a survey about their experience on the flight. What type of sample is this? a. Simple random sample b. Stratified random sample c. Multistage sample d. Cluster sample e. Convenience sample

b. Stratified random sample

A sampling method is biased if... a. It produces an estimate that is different than the true value in the population b. It produces estimates that vary quite a bit from the true value in the population c. It produces estimates that are consistently smaller or larger than the true value in the population d. It produces estimates that are different from sample to sample e. It produces estimates that wrong more than 50% of the time.

c. It produces estimates that are consistently smaller or larger than the true value in the population

During the summer, a group of 10 Desert Edge High School football players decides to eat a new type of protein bar each day before they lift weights. At the end of the summer, each of the players can lift more weight than he could at the beginning of the summer. Based on this study, is it reasonable to conclude that eating the new type of protein bar causes an increase in muscle a. No, the number of players in the study was too small. b. No, the group of football players wasn't randomly selected. c. No, it is possible that factors other than the bars might have caused the increase in muscle. d. Yes, each of the 10 players increased the amount of weight he could lift. e. Yes, because the football players ate the bars everyday

c. No, it is possible that factors other than the bars might have caused the increase in muscle.

For the track coaches study described in the previous question, which of the following best describes the conclusion that can be drawn. a. We can determine whether race times improve the runners in the new program, but we can not establish cause and effect. b. We can determine whether the new training program improved race times more than the standard program for any distance runner. c. We can determine whether the new training program improves race times more than the standard program for the distance runners in this study. d. We cannot draw any conclusions, since all the volunteers were already members of the coach's team. e. We cannot draw any conclusions because there was no control group.

c. We can determine whether the new training program improves race times more than the standard program for the distance runners in this study.

Some studies of the relationship between car color and frequency of accidents have found that red cars are more likely to be in an accidents that black cars, despite how visible they are. Some experts warn that we should not conclude that red cars are less safe than black cars, because of possible confounding. Which of the following best describes what this means? a. It can be hard to determine whether red cars or black cars are more visible on modern highways. b. Much of the data on the car color and accidents is contradictory, thus making it hard to draw definitive conclusions. c. Much of the data on car color and accidents is subject to bias, thus making it hard to draw definitive conclusions. d. It is not possible to separate the effect of car color from the type of people who choose to drive red cars. e. There are two many variables in traffic accidents to isolate the effect of car color.

d. It is not possible to separate the effect of car color from the type of people who choose to drive red cars.

A track coach wants to test the effectiveness of a new training program for distance runners. He selects his two fastest runners and, using a coin flip, randomly chooses one to participate in the new program. The other will continue with the standard training regimen. He then picks the next two fastest runners and randomly assigns one to each program. He repeats the process with all his runners, choosing the two fastest remaining each time. He then compares race times within each group of runners. What is the name for this kind of experimental design. a. Completely randomized design b. Randomized block designs, but not matched pairs c. Stratified random design d. Non-random pairs design e. Matched pairs design

e. Matched pairs design