Exam 6: Two-Way Tables

In a study of the link between high blood pressure and cardiovascular disease, a group of white men aged 35 to 64 was followed for five years. At the beginning of the study, each man had his blood pressure measured, and it was classified as either low systolic blood pressure (less than 140 mm Hg) or high blood pressure (140 mm Hg or higher). The following table gives the number of men in each blood pressure category and the number of deaths from cardiovascular disease during the five-year period. Based on these data, which of the following statements is correct?

A sociologist studying freshmen carried out a survey, asking (among other questions) how often students went out per week, how many hours they studied per day, and how many hours they slept at night. The table below provides the answers on the time slept and the time spent studying. Is there an association between the number of hours studied and the number of hours slept?

An administrator in charge of residential life services recently conducted a survey of undergraduate college students at a small university. A random sample of 300 students was selected from each class level (freshman, sophomore, junior, or senior). Each student was asked to complete and return a short questionnaire on the quality of campus residences. Some students returned the questionnaire; some did not. This is summarized in the table below. What percent of all students surveyed returned the questionnaire?

A study was conducted on horses to identify factors that might contribute to the formation of enteroliths-stones that form in the colon of the horse and eventually lead to blockage and death. The table below summarizes disease status by sex (gelding, mare, and stallion). How many conditional distributions for gender p (being a mare, given disease status) can be calculated for these data?

A sociologist studying freshmen carried out a survey, asking (among other questions) how often students went out per week, how many hours they studied per day, and how many hours they slept at night. The table below provides the answers on the time slept and the time spent studying. Among the students who studied 4 or more hours, what proportion slept less than 6 hours a night?

The following table describes the opinions of the 570 people that returned a residential life services questionnaire to researchers at a small university. Students were classified by class (freshman, sophomore, junior, or senior) and by their opinion of campus residence quality (high quality, medium quality, or low quality). Which marginal or conditional distribution would you use to determine the percent of all students who responded that are sophomores?

The following table describes the opinions of the 570 people who returned a residential life services questionnaire to researchers at a small university. Students were classified by class (freshman, sophomore, junior, or senior) and by their opinion of campus residence quality (high quality, medium quality, or low quality). What percent of all students who responded are sophomores?

In a recent round of layoffs in a company, the percent of employees 50 and older who were laid off was much higher than the percent younger than 50 who were laid off. However, when the data were analyzed separately in each job category, the percent of employees 50 and older who were laid off was lower than the percent of employees younger than 50 who were laid off in each job category. This reversal of direction of the association between age and being laid off, when job category is taken into account, is called:

Applicants looking for a job at a restaurant chain may apply to be a server or a kitchen worker. The table below summarizes the number of male and female applicants hired for the jobs for which they applied. The proportion of male applicants for a job as server that were hired is:

A company exploring ways to help its employees improve work/life balance conducted a survey of 360 of its workers that asked (among other things) about the number of hours typically spent on Facebook each day and about their stress level. Of the employees who spend the most time on Facebook, what percent have a high stress level?

A study was conducted on horses to identify factors that might contribute to the formation of enteroliths-stones that form in the colon of the horse and eventually lead to blockage and death. The table below summarizes disease status by sex (gelding, mare, and stallion). The proportion calculated as p = (62/137) = 0.4526 is:

A sociologist studying freshmen carried out a survey, asking (among other questions) how often students went out per week, how many hours they studied per day, and how many hours they slept at night. The table below provides the answers on the time slept and the time spent studying. Did students who studied 3 or more hours sleep less?

A sociologist studying freshmen carried out a survey, asking (among other questions) how often students went out per week, how many hours they studied per day, and how many hours they slept at night. The table below provides the answers on the time slept and the time spent studying. What proportion of students studied 3 hours or more?

A sociologist studying freshmen carried out a survey, asking (among other questions) how often students went out per week, how many hours they studied per day, and how many hours they slept at night. The table below provides the answers on the time slept and the time spent studying. What proportion of freshman slept at least 6 hours?

A study was conducted on horses to identify factors that might contribute to the formation of enteroliths-stones that form in the colon of the horse and eventually lead to blockage and death. The table below summarizes disease status, cases that have enteroliths by whether a horse has been altered (geldings have been castrated, mares and stallions have not been altered) and by whether the horse gets the majority of its feed as alfalfa. In the above table, when we look at the conditional probabilities of being a case, given being altered or not, we find that among those not fed alfalfa, horses that are not altered have a probability of being a case 3.3 times that of geldings. We find a similar ratio for the probabilities of horses fed alfalfa. When we calculate the ratio of those probabilities, combining the two tables when data are broken down by alfalfa feeding status, we find the probability of being a case, given a horse is not altered, is 6.4 times that of an altered horse. This is an example of:

The following table describes the opinions of the 570 people who returned a residential life services questionnaire to researchers at a small university. Students were classified by class (freshman, sophomore, junior, or senior) and by their opinion of campus residence quality (high quality, medium quality, or low quality). Of the students who feel campus residences are of high quality, what percent are seniors?

If X and Y are categorical variables, one way to identify whether there is a relationship between them is to:

Applicants looking for a job at a restaurant chain may apply to be a server or a kitchen worker. The table below summarizes the number of male and female applicants hired for the jobs for which they applied. The proportion of female applicants for a job as kitchen worker that were hired is:

The following table describes the opinions of the 570 people who returned a residential life services questionnaire to researchers at a small university. Students were classified by class (freshman, sophomore, junior, or senior) and by their opinion of campus residence quality (high quality, medium quality, or low quality). What percent of seniors feel that the quality of campus residences is not high?

A study was conducted on horses to identify factors that might contribute to the formation of enteroliths-stones that form in the colon of the horse and eventually lead to blockage and death. The table below summarizes disease status by sex (gelding, mare, and stallion). If you want to check whether there is an association between sex and case status, you should: