# Statistics for Health Services Management

## Matched Case Controls

Lecture

Assignment

1. These data show a list of 9 patients.  Two of the patients have received an experimental treatment.  Identify which of the patients in the following table could serve as controls for the two cases.  Select the possible controls randomly using the lowest random number.  Match on age.

2.  Patient ID Received Intervention Age Months to Fall Random Number Observation Period Follow-up Period 1 Yes 65 3 0.24 2 No 60 2 0.85 3 Yes 84 2 0.64 4 No 82 4 0.7 5 No 78 0.87 6 No 80 3 0.72 7 No 79 0.86 8 No 64 0.16 9 No 70 2 0.17
3. For the follow-up period in problem 1, show a Kaplan Meier survival curve.  For each month, show the percent of cases or controls that have not fallen since the start of the study.  Solution►
4. Establish the percent of days the following patient is in therapeutic range.  On days when blood pressure was not measured, assume that blood pressure is the same as the nearest data point less than 7 days away.  For all other days assume that the blood pressure is unknown.  Solution►
 Days Since Enrollment BP Therapeutic Range In range Lower Upper 0 125 120 140 Yes 20 150 120 140 No 60 130 120 140 Yes 70 110 120 140 No 90 130 120 140 Yes 120 135 120 140 Yes

For additional optional problem complete the following:

1. Repeat the matching but this time use as the criterion for matching the number of months of no falls during the observation period.  Does your answer differ from your answer to question 1, if so which is the better criterion to match, age or history of falls during the observation period?
2. For the cases and controls selected in problem 5, show a survival curve for data in the observation period.  Are these survival curves similar?  Should they be similar, why?