Odds Ratios and Chi-Square

Autumn Watkins

South University Online

PHE 5020

April 19, 2016

Part 2: Chi-Square

Bain, Willett, Hennekens, Rosner, Belanger, and Speizer (1981) conducted a study of the association between current postmenopausal hormone use and risk of nonfatal myocardial infarction (MI), in which 88 women reporting a diagnosis of MI and 1,873 healthy control subjects were identified from a large population of married female registered nurses aged thirty to fifty-five years. To test the hypothesis that there is no association between use of postmenopausal hormones and risk of MI, chi-square statistics need to be calculated.

The data are presented as follows:[sk1]

Table 2: Association between Postmenopausal Hormone Use and Risk of Nonfatal MI

Cases / Controls / Total
Currently use / 32 / 825 / 857
Never use / 56 / 1,048 / 1,104
Total / 88 / 1,873 / 1,961

Hypotheses: Null: H0: There is no association between use of post-menopausal hormones and risk of MI Alternative: Ha: There is an association between use of post-menopausal hormones and risk of MI [sk2]

Test Statistic: X^2 = 2.0167

P-value:p = 0.1556[sk3]

Decision: Assuming a 5% level of significance, the decision is to fail to reject the null hypothesis. [sk4]

Conclusion: There is insufficient evidence at the 0.05 level of significance to reject the claim that there is no association between use of post-menopausal hormones and risk of MI[sk5]

Steps Taken in Minitab to Conduct Analyses:

  • Entered data from assignment instructions [sk6]
  • Select Tables
  • Cross Tabulation and Chi-Square
  • Select data as “summarized data in a two-way table”
  • Entered cases and controls as columns containing the table
  • Before conducting the test, I changed the display to show the chi-square test for association and each cells contribution to chi-square
  • Select “Ok” to conduct test
  • Export file as a PDF document [sk7]

References

Bain, C., Willett, W., Hennekens, C. H., Rosner, B., Belanger, C., & Speizer,

F. E. (1981). Use of postmenopausal hormones and risk of myocardial

infarction. Circulation, 64(1), 42–46.

[sk1]Review comments from the first part of the assignment, they apply here as well.

[sk2]Good – I would like to see this set up as a report (refer to the rubric for this assignment). You must describe your methods. How did you obtain the test statistic and p-value?

[sk3]Correct but you must describe your methods

[sk4]What are the implications? What does it mean to “fail to reject the null hypothesis?

[sk5]Good, would like to see some additional discussion here and referencing back to the research question and problem.

[sk6]How were the data entered? Were they entered into columns? Were there column headings? Specifics are appreciated.

[sk7]Good, disregard comment above on methods; however, do remember that the report should follow a logical format in APA style. That means you start with an intro, methods, results, and discussion/interpretation. This should be a standalone document.