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Why are odds ratios and risk ratios different?
Odds Ratios and Relative Risks are often confused despite being unique concepts. The basic difference is that the odds ratio is a ratio of two odds (yep, it’s that obvious) whereas the relative risk is a ratio of two probabilities. (The relative risk is also called the risk ratio). Let’s look at an example.
When can odds ratios mislead?
The discrepancy between a relative risk reduction and the equivalent relative odds reduction (100×(1−odds ratio)%) can be misleading. When event rates are high (commonly the case in trials and systematic reviews) the relative odds reduction can be many times larger than the equivalent relative risk reduction.
What does odds ratio or relative risk mean?
The basic difference is that the odds ratio is a ratio of two odds (yep, it’s that obvious) whereas the relative risk is a ratio of two probabilities. (The relative risk is also called the risk ratio).
How to calculate odds ratio?
1) Calculate the odds that a member of the population has property “A”. Assume the person already has “B.” 2) Calculate the odds that a member of the population has property “A”. Assume the person does not have “B.” 3) Divide step 1 by step 2 to get the odds ratio (OR).
How do you calculate relative risk ratio?
Relative Risk is calculated by dividing the probability of an event occurring for group 1 (A) divided by the probability of an event occurring for group 2 (B). Relative Risk is very similar to Odds Ratio, however, RR is calculated by using percentages, whereas Odds Ratio is calculated by using the ratio of odds.
What are the stratum-specific odds ratios?
The following commands are issued to analyze the data: Single Table Analysis Stratum 1 Odds ratio = 1.70 Single Table Analysis Stratum 2 Odds ratio = 2.06 Thus, the strata-specific odds ratios are 1.70 and 2.06, respectively. We might now ask if it makes sense to summarize these two odds ratio with a single summary statistic.