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Module 2.2 Unit 6 Assignment 5

Total grades = 30 marks

Question 1 [15]

To study the possible association between oral contraceptive use and the occurrence of rheumatoid arthritis (RA), an investigator matched with respect to age and year of registry. Cases were women with confirmed diagnosis of RA and controls were women undergoing treatment at the same medical facility for other musculoskeletal conditions as subjects. The medical records of all subjects (prior to the date of first diagnosis were reviewed for evidence of oral contraceptive use. The results are summarized in the table below Controls (RA Absent)
Cases (RA Present)	OC Use	No OC Use	Totals
OC Use	20	20	40
No OC Use	50	10	60
Totals	70	30	100

a. Show formula of doing a matched analysis [2] b. Calculate and interpret the OR. [5] c. What is the purpose of matching in this study? [8]

Question 2 [15] In a study of pesticide use to the risk of miscarriage cases and controls are matched with respect to the age and year of registry at the particular medical facility. The table below shows the data from the study.

Controls (miscarriage Absent)
Cases miscarriage Present)	Pesticide Use	No Pesticide Use	Total pairs
Pesticide Use	30	30	60
No Pesticide Use	60	20	80
Totals	80	50	140

a). Calculate the odds ratio for women who had miscarriage who were exposed to pesticide [3] b). Was this association significant? (calculate the matched analysis chi-square) [6] c). Calculate the confidence intervals of this measure of effect you obtained in a above [6]

A. STANDARD STATISTICAL TABLES 355 Table A-4. Percentage points of the chi-square distribution (this table gives the values of x' for differing df that cut off specified proportions of the upper tail of the chi-square distribution) Area in upper tail df 10 05 01 001 2.71 3.84 6.63 10.83 4.61 5.99 9.21 13.82 6.25 7.81 11.34 16.27 7.78 9.49 13.28 18.47 9.24 11.07 15.09 20.52 10.64 12.59 16.81 22.46 12.02 14.07 18.48 24.32 13.36 15.51 20.09 26.13 14.68 16.92 21.67 27.88 15.99 18.31 23.21 29.59 11 17.28 19.68 24.73 31.26 12 18.55 21.03 26.22 32.91 13 19.81 22.36 27.69 34.53 14 21.06 23.68 29.14 36.12 15 22.31 25.00 30.58 37.70 16 23.54 26.30 32.00 39.25 17 24.77 27.59 33.41 40).79 18 25.99 28.87 34.81 42.31 19 27.20 30.14 36.19 43.82 20 28.41 31.41 37.57 45.32 21 29.62 32.67 38.93 46.80 22 30.81 33.92 40.29 48.27 23 32.01 35.17 41.64 49.73 24 33.20 36.42 12.98 51.18 25 34.38 37.65 44.31 52.62