Table of Contents

## What does the RR of 1.4 indicate?

A relative risk or odds ratio greater than one indicates an exposure to be harmful, while a value less than one indicates a protective effect. RR = 1.2 means exposed people are 20% more likely to be diseased, RR = 1.4 means 40% more likely. OR = 1.2 means that the odds of disease is 20% higher in exposed people.

**What is the difference between incidence rate ratio and incidence rate difference?**

“Incidence rate ratio (IRR) – Incidence rate ratio is the ratio of two incidence rates. The incidence rate is defined as number of events divided by the person-time at risk.

### How do you interpret incident rate ratio?

IRR Greater than 1: This indicates that the incident rate is greater in an exposed group compared to an unexposed group. For example, if smokers developed lung cancer at a rate of 7 per 100 person-years and non-smokers developed lung cancer at a rate of 1.5 per 100 person-years, then the IRR would be 7/1.5 = 4.67.

**How do you interpret a rate ratio less than 1?**

That is, a rate ratio of 1.0 indicates equal rates in the two groups, a rate ratio greater than 1.0 indicates an increased risk for the group in the numerator, and a rate ratio less than 1.0 indicates a decreased risk for the group in the numerator.

#### Can risk difference be greater than 1?

An OR value of 1 means no difference in odds between groups, and larger value than 1 means increased odds in exposed group, interpreted as a positive association between having disease and having exposure.

**What does a risk difference of 0 mean?**

The “Null” Values The null value is to the measure of association when the incidence is the same in the groups being compared. If this is the case, the risk ratio = 1, the risk difference = 0, and the excess relative risk = 0.

## What incidence rate tells us difference?

Abstract. The incidence rate difference (IRD) is a parameter of interest in many medical studies. For example, in vaccine studies, it is interpreted as the vaccine-attributable reduction in disease incidence. This is an important parameter, because it shows the public health impact of an intervention.

**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 doesâ€ť

### What does an odds ratio of 0.25 mean?

If a race horse runs 100 races and wins 25 times and loses the other 75 times, the probability of winning is 25/100 = 0.25 or 25%, but the odds of the horse winning are 25/75 = 0.333 or 1 win to 3 loses.

**What does a negative risk difference mean?**

decreased risk

A positive RD value means increased risk and a negative one means decreased risk by the exposure. RR is calculated as the risk of an exposed group divided by the risk of an unexposed group.

#### Is incidence rate difference a useful measure of intervention effect?

Recurrent events data are common in experimental and observational studies. It is often of interest to estimate the effect of an intervention on the incidence rate of the recurrent events. The incidence rate difference is a useful measure of intervention effect.

**What is the difference between a rate and a ratio?**

He has a master’s degree in writing and literature. In mathematics, a ratio indicates the number of times that a smaller number is contained within a larger number, while a rate expresses a ratio for two quantities measured in different units.

## What is the difference between a rate and a unit rate?

A rate is a special type of ratio in which the two terms are measured using different units. This is like paying for something by weight, where you’re comparing pounds to dollars. A unit rate is a rate where the denominator is one.

**What is the rate difference between highest and lowest categories?**

However, a rate difference is based on subtraction of incidence rates, so the units are retained. In the Nurses’ Health Study, the difference between highest and lowest weight categories was about 62.3 cases per 100,000 person-years (see figure to the right).