"Study: Asking Teens About Suicide Doesn't Lead Them to Take Their Lives" responded to a concern by many parents and schools that surveying teens about suicidal thoughts may have harmful repercussions by planting such ideas in their heads. The study "involved 2,342 students at six suburban New York high schools who answered two mental health questionnaires two days apart. Half the students-the experimental group-also received about 20 suiciderelated questions on both surveys. The questions included whether they had considered suicide and whether they thought it would be better if they were dead. The other half got suicide-related questions only on the second survey."3 Roughly 4 percent in both groups said they had had suicidal ideas since the first survey.
a. Describe the explanatory and response variables.
b. Which of these is known to equal 0.04? (There may be more than one.) n1, n2, X1, X2, , , p1, p2
c. Because the percentage with suicidal ideas was roughly the same for students in both groups, would the z statistic be close to zero, close to 2, or much larger than 2?
d. Would the P-value for a one-sided test be close to zero or close to 0.5?
e. The article mentions that each year 1,600 youngsters aged 15 to 19 succeed in committing suicide; since there are over 20 million in this age group, the proportion committing suicide is less than 1 in 10,000. Explain why it would be impractical to carry out a study where the response of interest is actually committing suicide-as opposed to thinking about suicide-after taking a survey.
f. The article also states that "the groups' scores on emotional-distress measures were similar before and after the first survey." Would a comparison be made using paired t, two-sample t, F, chisquare, or regression?
g. Which one of these focuses on data production?
1. The sample proportions were found to be almost identical.
2. If population proportions were equal, it would not be at all unlikely for sample proportions to be as different as those observed.
3. We conclude that, in general, asking teenagers about suicide doesn't lead them to have suicidal thoughts.
4. Within each of the selected classes, students were randomly assigned to receive suicide-related questions on both surveys or only on the second survey.
h. Which one of the statements in part (g) focuses on displaying and summarizing data?
i. Which one of the statements in part (g) focuses on probability?
j. Which one of the statements in part (g) focuses on statistical inference?