What if the odds ratio is less than 1?

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 0.8 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).

What does an odds ratio of 0.7 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 0.1 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 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).

Interpreting confidence intervals for the odds ratio

What does the 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”

What does an odds ratio of .75 mean?

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

The odds ratio for the predictor variable smoking is less than 1. This means that increasing from 0 to 1 for smoking (i.e. going from a non-smoker to a smoker) is associated with a decrease in the odds of a mother having a healthy baby.

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.

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.

What does an odds ratio of 0.05 mean?

An alpha of 0.05 means the confidence interval is 95% (1 – alpha) the true odds ratio of the overall population is within range. A 95% confidence is traditionally chosen in the medical literature (but other confidence intervals can be used).

What is a low odds ratio?

A low odds ratios indicates that the factor under examination is associated with a decrease, rather than an increase of risk relating to your outcome measure. Any significant departure from an odds ratio of 1 is of interest in understanding a factor's impact on outcomes.

What does a relative risk of 0.5 mean?

For example, when the RR is 2.0 the chance of a bad outcome is twice as likely to occur with the treatment as without it, whereas an RR of 0.5 means that the chance of a bad outcome is twice as likely to occur without the intervention. When the RR is exactly 1, the risk is unchanged.

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.

Is odds ratio less than 1 negative association?

The greatest the odds ratio, the more the risk factor favours the disease. If odds ratio is lower than 1, then there is a negative association. That is, your risk factor is counteracting the disease and people seems more likely to get the disease when your risk factor is not present than when it is present.

What are examples of low odds?

Low odds are something like 2-to-1 against. These odds mean something is somewhat likely to happen. The odds are low that Squiggly will ask for a chocolate dessert. Squiggly loves chocolate.

What is the rule of thumb for odds ratio?

But how big an effect is it? Epidemiologists use this very rough rule of thumb: 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.

How do you interpret the odds ratio less than 1 for a continuous variable?

Fortunately, the interpretation of an odds ratio for a continuous variable is similar and still centers around the value of one. When an OR is: Greater than 1: As the continuous variable increases, the event is more likely to occur. Less than 1: As the variable increases, the event is less likely to occur.

Can a ratio be less than 1?

A ratio is always less than 1.

What does a ratio of less than 1 mean?

Interpreting the Current Ratio

A ratio under 1.00 indicates that the company's debts due in a year or less are greater than its assets—cash or other short-term assets expected to be converted to cash within a year or less.

What is a normal odds 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 is 0.25 odds ratio?

Similarly a risk ratio of 0.25 is interpreted as the probability of an event with treatment being one-quarter of that without treatment. This may be expressed alternatively by saying that treatment decreases the risk of events by 100 × (1 –RR)% = 75%.

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 does an odds ratio of 0.50 mean?

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