Chapter 11, Problem 11.6AC

A statistics student at Pleasantville High School (PHS) looked at seat belt use by drivers. Customers were observed driving into a local convenience store. After the drivers left their cars, the student asked each driver several questions about seat belt use. In all, 80% of the drivers said that they always use seat belts. However, the student observed that only 61.5% of these same drivers were actually wearing a seat belt when they pulled into the store parking lot. Which of the following best explains the difference in the two percentages? (A) The difference is due to sampling variability. We shouldn't expect the results of a sample to match the truth about the population every time. (B) The difference is due to response bias. Drivers who don't use seat belts are likely to lie and say they do use seat belts. (C) The difference is due to undercoverage bias. The study included only customers of the convenience store and did not include all drivers in the population. (D) The difference…

A research article describes a study that investigated the relationship between depression and chocolate consumption. Participants in the study were 931 adults who were not currently taking medication for depression. These participants were screened for depression using a widely used screening test. The participants were then divided into two samples based on their test score. One sample consisted of people who screened positive for depression, and the other sample consisted of people who did not screen positive for depression. Each of the study participants also completed a food frequency survey. The researchers believed that the two samples were representative of the two populations of interest—adults who would screen positive for depression and adults who would not screen positive. The paper reported that the mean number of servings per month of chocolate for the sample of people that screened positive for depression was 8.37, and the sample standard deviation was 14.85. For the…

A researcher hypothesizes that personality type is related to heart disease. Type A people, who are competitive and impatient are more prone to heart diseases. Type B people, who are more relaxed, are less likely to have heart problems. The following data about personality type and heart disorder are from a random sample.  No heart disease heart disease total Type A 32 18 50 Type B 128 22 150 total 160 40                                          Do these data support that there is a significant relationship between personality type and heart disease? Test at the .05 level of significance. Compute the phi-coefficient to measure the strength of the relationship.