“the odds of an event is the number of those who experience the event divided by the number of those who do not. … So, for example, an odds ratio of 0.75 means that in one group the outcome is 25% less likely. An odds ratio of 1.33 means that in one group the outcome is 33% more likely.”

Also, What does an odds ratio of 2.0 mean?

An OR of 2 means there is a 100% increase in the odds of an outcome with a given exposure. Or this could be stated that there is a doubling of the odds of the outcome. Note, this is not the same as saying a doubling of the risk.

Hereof, How do you know if odds ratio is statistically significant?

If the p-value is equal to or less than a predetermined cutoff (usually 0.05, or a 5 in 100 probability that the finding is due to chance alone), the association is said to be statistically significant. If it is greater than the predetermined cutoff, the association is said to be not statistically significant.

Also to know What is the odds ratio formula? Odds Ratio = (odds of the event in the exposed group) / (odds of the event in the non-exposed group) If the data is set up in a 2 x 2 table as shown in the figure then the odds ratio is (a/b) / (c/d) = ad/bc. The following is an example to demonstrate calculating the odds ratio (OR).

What is considered a strong odds ratio?

An odds ratio of 4 or more is pretty strong and not likely to be able to be explained away by some unmeasured variables. … An odds ratio between 1.0 and 1.5 is at best suggestive of lines for further research.

23 Related Questions Answers Found

What does an odds ratio of one mean?

An odds ratio of 1 indicates that the condition or event under study is equally likely to occur in both groups. An odds ratio greater than 1 indicates that the condition or event is more likely to occur in the first group.

What does an odds ratio of 0.4 mean?

For example, the odds ratio of 0.4 could mean, in numerical terms it means that for every 10 females without bowel cancer there are 20 who does, while in males, for every 10 individuals who do not have the tumor there are 50 who does

How do you adjust odds ratio?

Age: The adjusted odds ratio for age is calculated as e.045 = 1.046. This means the odds of having a baby with low birthweight are increased by 4.6% for each additional yearly increase in age, assuming the variable smoking is held constant. For example, suppose mother A and mother B are both smokers.

What is the difference between risk ratio and odds ratio?

The relative risk (also known as risk ratio [RR]) is the ratio of risk of an event in one group (e.g., exposed group) versus the risk of the event in the other group (e.g., nonexposed group). 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.

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.

Which is better odds ratio OR relative 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) more than 1.0 indicates an increase in risk (or odds) among the exposed compared to the unexposed, whereas a RR (or OR) <1.0 indicates a decrease in risk (or odds) in the exposed group.

What if odds ratio is less than 1?

When the odds ratio is lower than 1, the likelihood of having the outcome is XX% lower (XX% = 1-Odds ratio). For e.g. if odds ratio is 0.70, then there is a 30% lower likelihood of having the outcome.

What does odds ratio of Infinity mean?

An odds ratio of infinity means that the lists are highly dependent (not independent), as one is contained in other.

How do you interpret odds ratios greater than 1?

An odds ratio of exactly 1 means that exposure to property A does not affect the odds of property B. An odds ratio of more than 1 means that there is a higher odds of property B happening with exposure to property A. An odds ratio is less than 1 is associated with lower odds.

What is the odds ratio in logistic regression?

For example, in logistic regression the odds ratio represents the constant effect of a predictor X, on the likelihood that one outcome will occur. The key phrase here is constant effect. In regression models, we often want a measure of the unique effect of each X on Y.

How do you interpret odds ratios less than 1?

When the odds ratio is lower than 1, the likelihood of having the outcome is XX% lower (XX% = 1-Odds ratio). For e.g. if odds ratio is 0.70, then there is a 30% lower likelihood of having the outcome.

How do you interpret risk ratios?

A risk ratio greater than 1.0 indicates an increased risk for the group in the numerator, usually the exposed group. A risk ratio less than 1.0 indicates a decreased risk for the exposed group, indicating that perhaps exposure actually protects against disease occurrence.

When should odds ratio be used?

When is it used? Odds ratios are used to compare the relative odds of the occurrence of the outcome of interest (e.g. disease or disorder), given exposure to the variable of interest (e.g. health characteristic, aspect of medical history).

What does an odds ratio of 0.5 mean?

An odds ratio of 0.5 would mean that the exposed group has half, or 50%, of the odds of developing disease as the unexposed group. In other words, the exposure is protective against disease. … You have to report OR with its confidence interval value.

What does a relative risk of 1.5 mean?

• This means if the relative risk was 1.5, people in Group A would be 50% more likely than people in all other groups to die from a cause. • Or if the relative risk were 3.0, people in Group A would be three times as likely as people from other groups to die from a cause.

How do you combine odds ratios?

Typically you combine by taking the weighted average of the log of the odds ratio and then exponentiating. If the sizes of the data sets are roughly equal for your odds ratios then it’s the average of the log odds.

How do you read odds ratio?


Using Betting Odds to Calculate Probability

  1. 9/1 can be calculated as 1 / (9 + 1) = 0.10 – There is a 10% chance that the event will happen.
  2. 4/1 can be calculated as 1 / (4 + 1) = 0.20 – There is a 20% chance that the event will happen.

What does an odds ratio of 0.99 mean?

From probability to odds

Our starting point is that of using probability to express the chance that an event of interest occurs. So a probability of 0.1, or 10% risk, means that there is a 1 in 10 chance of the event occurring. … As p increases, the odds get larger and larger. For example, with p=0.99, odds=0.99/0.01=99.

What is the difference between odds ratio and chi square?

As Lluis’s mentioned in his answer, you would use a chi-square to TEST if an association exists. On the other hand, you would use an odds ratio, relative risk, hazard rate, etc. to MEASURE or quantify the association between a risk factor/covariate and an outcome.

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