Quiz 6, Module Cohort
6. Calculation of the risk ratio from person-time information. [Aschengrau & Seage, Chapter 3]
The data collected by your team yield the following information:
- Number of cases among exposed - 74
- Number of cases among unexposed - 120
-
Total number of exposed individuals - 1,900
- Low exposure group - 1,000
- Medium exposure group - 650
- High exposure group - 250
- Total number of unexposed individuals - 7,400
- How would you present the data in the 2x2 table?
- Calculate the risk of disease among the exposed. The formula for calculating risk is: (Number of exposed cases per 2-yr time period) / (Total number of exposed persons per 2-yr time period)
- Calculate the risk of disease among unexposed
- Calculate risk ratio
- Interpret your findings
none:
| Disease + | Disease - | Total | |
|---|---|---|---|
| Exposed | 74 | 1,900-74 | 1,900 |
| Unexposed | 120 | 7,400-120 | 7,400 |
| Disease + | Disease - | Total | |
|---|---|---|---|
| Exposed | 74 | 1,826 | 1,900 |
| Unexposed | 120 | 7,280 | 7,400 |
none:
The formula for calculating risk is: (Number of exposed cases per 2-yr time period) / (Total number of exposed persons per 2-yr time period)
= 74/1,900
= 0.0389 (or 39 cases per 1,000 exposed per 2-yr time period)
The risk of developing Susser Syndrome among those exposed to SUPERCLEAN (for at least 6 months) is 39 cases per 1,000 exposed per 2 years.
none:
(Number of unexposed cases during 2-yr time period) / (Total number of unexposed persons during 2-yr time period)
= 120/7,400
= 0.0162 (or 16 cases per 1,000 unexposed per 2-yr time period)
The risk of Susser Syndrome among those unexposed to SUPERCLEAN (for at least 6 months) is 16 cases per 1,000 exposed per 2 years.
none:
(Risk of disease among the exposed) / (Risk of disease among the unexposed)
= 0.0389/0.0162
= 2.40
none: Those who were exposed to chemicals involved in the SUPERCLEAN production for at least 6 months have a 2.40 times higher risk of developing Susser Syndrome than those who were not exposed to SUPERCLEAN production.
