What is the rule of thumb for odds ratio?

As a general rule of thumb, it is acceptable to interpret the odds ratio as a risk ratio when the risk (or prevalence) of the outcome in the reference group is less than 10% [1, 2]. In most cases, the odds ratio and risk ratio are similar when the outcome is this rare (Figure 1).

What is considered a good odds ratio?

For example, an odds ratio of 1.2 is above 1.0, but is not a strong association. An odds ratio of 10 suggests a stronger association.

What does an odds ratio of 1.5 mean?

It means that the odds of a case having had exposure #1 are 1.5 times the odds of its having the baseline exposure. This is not the same as being 1.5 times as probable: odds are not the same as probability (odds of 2:1 against means a probability of 13).

What is the threshold for odd ratio?

An odds ratio greater than 1 indicates that the condition or event is more likely to occur in the first group. And an odds ratio less than 1 indicates that the condition or event is less likely to occur in the first group. The odds ratio must be nonnegative if it is defined.

What does an odds ratio of 0.5 mean?

A RR of 0.5 means the risk is cut in half.

Medical Statistics - Part 7: OR and RR in Observational Studies

What does an odds ratio OR of 0.70 mean?

If the Odds ratio is 0.7 then it indicates a protective effect - I.e a reduced odds of exposure in case vs control group. That reduced risk is 1-odds so will be 30 percent reduced risk fo exposure. statistical significance is linked to the p-value or CI- which we cannot infer from only the odds ratio.

What does an odds ratio of 0.80 mean?

(Example: If the probability of an event is 0.80 (80%), then the probability that the event will not occur is 1-0.80 = 0.20, or 20%. The odds of an event represent the ratio of the (probability that the event will occur) / (probability that the event will not occur).

What happens if odds ratio is less than 1?

If a predictor variable in a logistic regression model has an odds ratio less than 1, it means that a one unit increase in that variable is associated with a decrease in the odds of the response variable occurring.

Can an odds ratio be higher than 2?

As stated above, the odds ratio is a ratio of 2 odds. As odds of an event are always positive, the odds ratio is always positive and ranges from zero to very large. The relative risk is a ratio of probabilities of the event occurring in all exposed individuals versus the event occurring in all non-exposed individuals.

What is the odds ratio for dummies?

What is an odds ratio? An odds ratio (OR) is a measure of association between an exposure and an outcome. The OR represents the odds that an outcome will occur given a particular exposure, compared to the odds of the outcome occurring in the absence of that exposure.

What does an odds ratio of 0.2 mean?

An odds of 0.2 however seems less intuitive: 0.2 people will experience the event for every one that does not. This translates to one event for every five non-events (a risk of one in six or 17%).

What does an odds ratio of less than 1.0 mean?

“An OR of less than 1 means that the first group was less likely to experience the event. However, an OR value below 1.00 is not directly interpretable. The degree to which the first group is less likely to experience the event is not the OR result.

What does an odds ratio of .98 mean?

The reported odd ratio of 0.98 at less than 1 indicates that for every additional parameter of the tested independent variable, they were . 98 times likely to report the likelihood of the test question.

Are 5 to 1 odds good?

5 to 1 Implied Probability

The 5-1 betting odds probability is an 83.33 per cent probability of a particular outcome and a 16.67 per cent probability of another outcome. The 5/1 odds implied probability means your selection has a 16.67% chance of winning and an 83.33% chance the selection will lose.

Is 1.5 odds good?

Setting the line at just 1.5 does mean that these two teams are extremely close. This is what is called a “spread” bet, or “betting against the spread.” This is a very common bet in basketball and football games, but it is seen in other sports as well.

What is the odds ratio for risk?

The odds ratio (OR) is the ratio of odds of an event in one group versus the odds of the event in the other group. An RR (or OR) of 1.0 indicates that there is no difference in risk (or odds) between the groups being compared.

What does an odds ratio of 5.2 mean?

Consequently, an odds ratio of 5.2 with a confidence interval of 3.2 to 7.2 suggests that there is a 95% probability that the true odds ratio would be likely to lie in the range 3.2-7.2 assuming there is no bias or confounding.

What happens if odds ratio crosses 1?

Most studies report the 95% confidence interval (95%CI). If the confidence interval crosses 1 (e.g. 95%CI 0.9-1.1) this implies there is no difference between arms of the study.

Can odds ratio be over 100%?

Probability values can only range from 0 to 1 (0% to 100%), whereas odds can take on any value.

What does an odds ratio of 0.1 mean?

From probability to odds

So a probability of 0.1, or 10% risk, means that there is a 1 in 10 chance of the event occurring.

Why can odds ratios be misleading?

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.

When can odds ratios mislead?

Substantial discrepancies between the odds ratio and the relative risk are seen only when the effect sizes are large and the initial risk is high.

What is 75 odds ratio?

Thus, an odds ratio of . 75 translates into a failure rate of 15.8% in the treatment group relative to an assumed failure rate of 20% in the control group. This translation of odds ratios into an easily understand metric is commonly used in meta-analyses of odds ratios.

Can an odds ratio be negative?

The odds ratio is always positive, although the estimated log odds can be positive or negative (log odds of −0.2 equals odds ratio of 0.82 = exp(−0.2)).

How do you interpret 0.75 odds ratio?

2c) A risk ratio of 0.75 means there is an inverse association, i.e. there is a decreased risk for the health outcome among the exposed group when compared with the unexposed group. The exposed group has 0.75 times the risk of having the health outcome when compared with the unexposed group.