# 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.

14 questions
Filter by
Sorted by
Tagged with
1answer
13 views

### Calculating risk difference with covariate

How do I calculate a risk difference for a binary outcome that takes into account a covariate? I want to compare accuracy of a skilled and unskilled tester at detecting 7 different types of tumors. ...
0answers
28 views

### Is there a minimum variance for metafor::rma.mv()?

I want to run a three-level meta-analysis model of observed data with Measurement as a nested level of Study (independent samples, only source of covariance being the study group measuring them) using ...
1answer
122 views

### Calculating risk difference and number needed to treat from hazard ratio in meta-analysis

If you have primary data, there exist several ways to calculate a risk difference (RD) or number needed to treat (NNT) from time-to-event data (see e.g. following pmid: 29955580, 31626655). However, I ...
1answer
26 views

### 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: ...
1answer
26 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 ...
1answer
113 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 ...
2answers
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 ...
1answer
48 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 ...
2answers
87 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' ...
0answers
56 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 ...
0answers
71 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 ...
1answer
594 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 ...
2answers
516 views

### odds ratio: the purpose and interpretation

Could someone please explain the purpose of the odds ratio and how it could be interpreted (i.e., the origin of their usage is in primary interest for me)? Why don't people simply use the difference ...
1answer
2k views

### Two methods to calculate the confidence interval for number needed to treat yield different results

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) $NNT=1/|RD|$ ...