Question

Applications that do violate the OLS assumptions for inference. All of the examples in this section have at least one violation of the OLS assumptions for inference. Begin by identifying the response and explanatory variables. Then, identify which OLS assumption(s) are violated.

1. Clinical Trial I. A Phase II clinical trial is designed to compare the number of patients getting relief at different dose levels. 100 patients get dose A, 100 get dose B, and 100 get dose C.
2. Canoes and zip codes. For each of over 27,000 overnight permits for the Boundary Water Canoe area, the zip code for the group leader has been translated to the distance traveled and socioeconomic data. This data is used to create a model for the number of trips made per zip code.
3. Clinical Trial II. A randomized clinical trial investigated postnatal depression and the use of an estrogen patch. Patients were randomly assigned to either use the patch or not. Depression scores were recorded on 6 different visits.
4. Elephant mating. Researchers are interested in how elephant age affects mating patterns among males. In particular, do older elephants have greater mating success, and is there an optimal age for mating among males? Data collected includes, for each elephant, age and number of matings in a given year.

Answer 1

1. Response variable-Number of patients.

Explanatory variables-Dose levels; where doses are A,B and C

2. Response variable-Number of trips per zip code

  Explanatory variables-Zip code

3. Response variable-Depression Scores

Explanatory variables- Use estrogen patch : Yes/No

4. Response variable-Mating patterns in male

Explanatory variables-Age of elephant