STAT 150 “Studies and Conclusions” Assignment due Tues Oct 20
A study published in the January 2008 issue of the journal Behavioral Sleep Medicine involved a
survey of 120 students at St. Lawrence University, a small liberal arts college
in upstate
a) Identify the explanatory and response variables in this study. Classify each as categorical or quantitative.
b) Is this an observational study or a randomized experiment? Explain how you know.
c) Suppose that the difference between these two averages is shown to be statistically significant. Can you legitimately conclude that pulling all-nighters causes a student’s GPA to decrease? If so, explain why. If not, identify a potential confounding variable, and explain how it provides an alternative explanation for why the all-nighter group would have a significantly lower average GPA.
An article about handwriting appeared in the October 11, 2006 issue of the Washington Post. The article mentioned that among students who took the essay portion of the SAT exam in 2005-06, those who wrote in cursive style scored significantly higher on the essay, on average, than students who used printed block letters.
d) Identify the explanatory and response variables in this study. Classify each as categorical or quantitative.
e) Is this an observational study or an experiment? Explain briefly.
f) Would you conclude from this study that using cursive style causes students to score better on the essay? If so, explain why. If not, identify a potential confounding variable, and explain how it provides an alternative explanation for why the cursive writing group would have a significantly higher average essay score.
The article also mentioned a different study in which one essay was given to many graders all. But some graders were shown a cursive version of the essay and the other graders were shown a version with printed block letters. Researchers randomly decided which version the grader would receive. The average score assigned to the essay with the cursive style was significantly higher than the average score assigned to the essay with the printed block letters.
g) What conclusion would you draw from this second study? Be clear about how this conclusion would differ from that of the first study, and why that conclusion is justified.