STAT 301 HW17 due Mon Nov 9

You may work with one partner on this assignment, submitting one report with both names, provided that both students contribute substantially to the work. Word-processed reports are preferred to hand-written ones. Please copy/paste relevant computer output into your report as appropriate.

Memorizing Letters?

Consider the data that we gathered in class about memorizing letters, which are in the Minitab worksheet MemoryScores301F09.mtw. (Click on the filename to open it, as long as you are on a computer that has Minitab.)

a) Identify the explanatory and response variables. Also classify each as categorical or quantitative.

b) Is this an observational study or a randomized experiment? Explain how you know.

c) Create dotplots for comparing the memory scores between the two groups on a common axis and scale (Graph> Dotplot). Submit these graphs, and comment on what they reveal about the conjecture that those in the JFK group would tend to memorize more letters than those in the JFKC group.

d) Calculate the mean and median of the number of letters memorized for each group (Stat> Basic Statistics> Display descriptive statistics). Do these summary values indicate that the JFK group did indeed perform better than the JFKC group?

e) Use the applet (available here) to simulate a randomization test for assessing whether the data provide statistically significant evidence that the grouping of letters causes an increase in memory performance. Submit a screen capture of the resulting dotplot, and answer four questions:

i) Describe the null model that underlies this simulation analysis.

ii) Explain what variable is displayed in the dotplot.

iii) Describe what the dotplot reveals.

iv) Report the approximate p-value.

f) Summarize your conclusion in the context of this study. Include an explanation of the reasoning process behind your conclusion. Be sure to address the issues of causation (i.e., is a cause-and-effect conclusion warranted?) and generalizability (i.e., how broadly can you legitimately generalize your conclusion?), as well as the issue of statistical significance.