Explore the Data

To compare proportions across groups, we often start with a two-way table.

Dolphin GroupNature GroupTotal
Showed substantial improvement 10313
Did not show substantial improvement  51217
Total151530

(c) Calculate the difference in the conditional proportions with substantial improvement between the two explanatory variable groups.

Of the 15 subjects in the Dolphin group, what proportion showed substantial improvement?

Of the 15 subjects in the Nature group, what proportion showed substantial improvement?

Calculate the difference in these two proportions (dolphin - nature).

To compare two groups on a categorical variable, the best graphs to use are a segmented bar graph or a mosiac plot where each explanatory variable group has its own column and the graph shows the distribution of the response variable within each group.

(e) Use the applet below to create bar graphs comparing the yawning rates between the two groups.

  • Check the box next to 2x2: to display an empty 2x2 table.
  • Type in the four cell counts
    • Group A = Dolphin
    • Group B = Nature
    • Success = Improved
    • Failure = Not improved
  • Press Use Table.
  • Check the Show Table box to confirm your data entry and conditional proportion calculations.
  • Use the pull-down menu above the graph to toggle to a Mosaic plot.

Confirm your calculation of the difference in conditional proportions.

(d) Copy and paste your segmented bar graph or mosaic plot to the designated area of your lab report. In the Word file, you should write a sentence introducing the graph output to the reader (or at least give it a nice title).

(e) Do the data appear to support the claim that dolphin therapy is more effective than the nature program?

BackNext