# Questions tagged [risk-difference]

The risk-difference is the difference between the probabilities of an event under two conditions (ie, p1-p2). The RD has a possible range of [-1, 1]. It is a common measure of effect size in biomedical research.

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### In a meta-analysis, can you back calculate estimated group proportions from risk difference?

In a meta-analysis of the risk difference, does it make sense to apply the weights & back calculate the expected proportions in each group? For example, if you had the following: ...
13 views

### How to use proc logistic to estimate probability difference — or common risk difference [duplicate]

I try to use proc logistic regression to estimate the probability difference between placebo and treatment group. It gives me odds ratio difference, how can I change to risk difference?    Also any ...
25 views

### What's “the clinically important absolute scale”?

In this article, the authors used the sentence "...risk difference (i.e., treatment effect on the clinically important absolute scale)". What did they mean by "clinically important ...
86 views

### Odds Ratio Vs. Risk Ratio

Relative risk, odds ratio, risk ratio, risk difference - these are all measures of the direction and the strength of the association between two categorical variables. Can I use any of these four ...
2k views

### Is there any better alternative to Linear Probability Model?

I read here, here, here, and elsewhere that linear probability model (LPM) might be used to get risk differences when the outcome variable is binomial. LPM has some advantages such as ease of ...
47 views

### Is there a two-by-two contingency table dataset where an Odds Ratio estimate would work and a Risk Ratio would fail?

I am wondering if there is an example of a two-by-two contingency table dataset where an Odds Ratio estimate would work and a Risk Ratio would fail, or vice versa? In additional are there cases where ...
86 views

### Using patient characteristics to predict disease and confront with per hospital real cases

We have a large, nationwide prevalence study about the prevalence of healthcare-associated infections (HAI). We need to see if hospitals have more or less HAI than expected by their patients' ...
51 views

### Correct model for comparing frequencies of comorbidities, large numbers

Here is what my group wants to do: Query a database for cases of several disorders, including Disorder A and Disorder B. Of those cases, specifically query for cases of Disorder A comorbid with each ...
69 views

### Why do we use the equal-means assumption in estimating the SE in a z-test but not a t-test?

When we perform a z-test for the difference in proportions between two groups of binary data, we use the fact that under the null hypothesis the proportions are assumed equal in order to estimate the ...
508 views

### Absolute risk and NNT from logistic regression

I fitted a Logistic regression with a number of variables, and was asked about the absolute risk (AR) and number needed to treat (NNT) for one of the variable with the outcome. I understand how to ...
Assume that two drugs were tested. The risk of death for drug 1 is $p_1$ and the risk for drug 2 is $p_2$. We define: Risk difference (RD) $RD=p_1-p_2$ The number needed to treat (NNT) $NNT=1/|RD|$ ...