Exercises

1. Using the dataset "Assumptions met," examine the effects of varying the range on each of the following:
  1. slope
  2. standard error of the estimate
  3. Pearson's r
  4. the corrected value of Pearson's r
2. Using the dataset strength,
  1. Find the correlation if only subjects in the upper-half of the grip strength distribution. (Use the top 74 subjects).
  2. Is it higher or lower than the correlation in the full sample?
  3. How does the corrected correlation compare with the correlation in the full sample?
  4. Find the correlation for the remaining 73 subjects.
  5. Find the correlation for those subjects scoring below 80 or above 140 on grip strength. Compare this correlation to the full-sample correlation and the corrected correlation.
3. For the SAT data,
  1. Compare the standard error of the estimate for subjects scoring below 500 on the SAT Verbal with the standard error of the estimate for subjects scoring above 500.
  2. Compare the slopes for these two portions of the sample.
  3. How do the answers to (a) and (b) above affect the corrected r for the two portions of the sample. Explain why.