What is the odds ratio for dummies?

The odds ratio is the “measure of association” for a case-control study. It quantifies the relationship between an exposure (such as eating a food or attending an event) and a disease in a case-control study.

What is the odds ratio in simple terms?

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 1 OR 1 mean?

An odds ratio of less than 1 implies the odds of the event happening in the exposed group are less than in the non-exposed group. An odds ratio of exactly 1 means the odds of the event happening are the exact same in the exposed versus the non-exposed group.

What does an odds ratio of 1.25 mean?

“For example, if the Odds Ratio was, for example, 1.25, it would mean that the fact of being a woman is a risk factor for cancer because for every 10 women without a tumor there would be 50 with it, while for every 10 healthy men there would be only 40 diseased”.

What does an odds ratio of 0.8 mean?

Examples. RR of 0.8 means an RRR of 20% (meaning a 20% reduction in the relative risk of the specified outcome in the treatment group compared with the control group).

NCCMT - URE - Odds Ratios

What does an odds ratio of 0.33 mean?

In the spades example, given that the probability of drawing a spade is 1/4, take 1/(4-1) = 1:3 odds or odds = 0.33. Statistical Significance. If an odds ratio (OR) is 1, it means there is no association between the exposure and outcome.

What does a odds ratio OR greater than 1.0 mean?

Greater than 1.0 indicates that the odds of exposure among case-patients are greater than the odds of exposure among controls. The exposure might be a risk factor for the disease. • Less than 1.0 indicates that the odds of exposure among case-patients are lower than the odds of exposure among controls.

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.

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.

What do odds of 5 to 1 mean?

5-1 Betting Odds means that out of 6 possible outcomes, the 5/1 odds are that there will be 5 of one kind of outcome and 1 of another kind of outcome. The 5-1 odds calculation means for every 6 betting events your selection should win 1 time and on 5 occasions the selection will not win.

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.

What does 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.

What is an example of an odds ratio less than 1?

"When you are interpreting an odds ratio (or any ratio for that matter), it is often helpful to look at how much it deviates from 1. 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."

What is an example of an odds ratio?

The odds ratio is calculated by dividing the odds of the first group by the odds in the second group. In the case of the worked example, it is the ratio of the odds of lung cancer in smokers divided by the odds of lung cancer in non-smokers: (647/622)/(2/27)=14.04.

How do you interpret bet odds?

Whereas negative (-) odds tell you what you have to bet on the favorite to win $100, positive (+) odds tell you how much you'll win for every $100 you wager on the underdog. So, a team with odds of +120 would payout $120 for every $100 wager.

Is The odds ratio positive OR negative?

To conclude, the important thing to remember about the odds ratio is that an odds ratio greater than 1 is a positive association (i.e., higher number for the predictor means group 1 in the outcome), and an odds ratio less than 1 is negative association (i.e., higher number for the predictor means group 0 in the outcome ...

Which odds ratio is strongest?

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 bigger than 2 and less than 4 is possibly important and should be looked at very carefully.

Does odds ratio indicate 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.

Can an odds ratio be 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 0.70 mean?

In the study by Lin et al, the probability of the event was 59% and, using the calculation proposed by Davis et al,² we can estimate that the odds ratio of 0.70 is equivalent to a relative risk of 0.85—that is, the odds ratio is 18% smaller than the relative risk.

What do the odds 9 to 5 mean?

9-5 Betting Odds means that out of 14 potential outcomes, the 9/5 odds are that there will be 9 of one kind of outcome and 5 of another kind of outcome. The 9-5 odds calculation means for every 14 betting events your selection should win 5 times and on 9 occasions the selection will not win.

What does odds greater than 2.0 mean?

Decimal odds below 2.0 are less than even money odds, meaning the potential return will be less than your stake. Odds above 2.0 are positive odds, meaning your potential return will be more than your stake. Decimal odds are also the most economical way to bet parlays, because the true odds will be calculated.

What does an odds ratio of 0.15 mean?

Because it is an OR, we must say that for every 0.15 (or 15) persons who experience the event in the experimental group, 1 person (or 100 persons) will experience the event in the control group. That is, the odds are 15 to 100.

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.

What does an odds ratio of 0.91 mean?

In general the relationship between a factor increase and the percentage change is (f - 1) * 100%. So an odds ratio of 0.91 corresponds to a (0.91 - 1)*100% = -9% change in odds for a unit increase in factor B, or a 9% decrease in the odds for a unit change in factor B.