# 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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### Statistical Measurement to Compare Risk Tables of Survival Curves

Disclaimer: not a statistician ;-) Background I have time-to-event data and a computational model that generates time-to-event data. The idea is that the modeled data mimics the actual data. I can ...
11 views

### risk ratio and risk difference consistent?

how do you determine whether the results for risk difference and risk ratio are consistent? Risk difference = 0.02, 95% CI [-1.05, 0.1] Risk ratio = 1.1, 95% CI [0.82, 1.5] Study on whether or not ...
1 vote
28 views

### Adjusted risk difference and negative confidence interval

I was reading this article. The authors used mixed effects logistic regression and presented their results as adjusted risk difference. I noticed that some of the confidence interval were negative, I ...
30 views

### How can I estimate the risk difference confidence interval with the standard errors of the risks?

I have two risks estimated from imputed data, so I cannot say I have a1 events in the exposed and a0 events in the unexposed, as each data set is different. The output of the function are risks and ...
1 vote
38 views

### Risk difference with patient-years incidence rates

I am aware that you can compute risk differences as the difference of risk between two treatment arms $( (\text{No. events}_1/ N_1) - (\text{No. events}_2 / N_2))$. However, can I estimate the same ...
373 views

### Bootstrap for random effects logistic regression to get CI for difference in proportions

Let's say I have two observations of a binary variable per patient on two different treatments for a sensible number of patients, some variable like age, and I'm fitting a model like this in R: ...
26 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. ...
1 vote
43 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 ...
245 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 ...
29 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: ...
33 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 ...
153 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 ...
59 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 ...
92 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' ...
60 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 ...
1 vote
77 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 ...
1 vote
669 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) $NNT=1/|RD|$ ...