Why do we use odds ratio for Case Control?
The odds ratio is calculated using the number of case-patients who did or did not have exposure to a factor (such as a particular food) and the number of controls who did or did not have the exposure. The odds ratio tells us how much higher the odds of exposure are among case-patients than among controls.
Why is odds ratio better than relative risk?
The relative risk (RR), also sometimes known as the risk ratio, compares the risk of exposed and unexposed subjects, while the odds ratio (OR) compares odds. A relative risk or odds ratio greater than one indicates an exposure to be harmful, while a value less than one indicates a protective effect.
How are odds ratios and risk ratios related?
Odds ratios (OR) are commonly reported in the medical literature as the measure of association between exposure and outcome. However, it is relative risk that people more intuitively understand as a measure of association. Relative risk can be directly determined in a cohort study by calculating a r …
When to use ” odds ” instead of ” risk “?
The term “odds” is often used instead of risk. “Odds” refers to the probability of occurrence of an event/probability of the event not occurring. At first glance, though these two concepts seem similar and interchangeable, there are important differences that dictate where the use of either of these is appropriate.
Why do we need to calculate the difference in proportions?
Of course if our data is a sample, the calculated difference in proportions is just an estimate. If we were take another sample and calculate the difference in proportions we would get a different estimate. So we need to calculate a standard error for the difference in proportions to give us some indication of its variability.
Which is better a percent increase or a risk ratio?
Percent increase = (Risk Ratio lower bound – 1) x 100 Percent decrease = (1 – Risk Ratio upper bound) x 100 It’s worth stating again: when comparing two proportions close to 1 or 0, the risk ratio is usually a better summary than the raw difference.