# Tagged Questions

The relative risk (also called 'risk ratio') is the quotient of the probabilities of an event under two conditions (ie, p1/p2). The RR has a possible range of (0, +infinity). It is a common measure of effect size in biomedical research.

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### Confidence interval for a relative risk when one proportion is 0

I am analysing data from a small study. There are two treatment groups and for each, one notes success and failures. For one of the groups, the number of successes is 0. I did an exact significance ...
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### Measures of effect size for chi-squared tests

What are the different measures of effect size used for chi-squared tests / binomial data? I'm already at least somewhat familiar with the phi coefficient and odds ratio. I've heard of Cramer's V and ...
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### How to estimate Relative Risks in Multivariate Binary Logistic Regression Models, instead of Odds Ratios?

All software programs I have tried report only odds ratios (ORs) for binary logistic regression predictors (as exponential of the betas). I am interested to know how can I compute the relative risk ...
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### How do I interpret the figure output from package dlnm in R?

I am performing distributed non-linear lag models in R. I got the figure result of dlnm as shown in the vignette (pdf) on page 13: The X-axis is lag, which I ...
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### Changing the effect measure flips the estimated direction in a Bayesian difference-in-difference analysis

Within a Bayesian model, I have binomial rate parameter estimates for 4 groups, A1, A2, B1, B2 (4 parameters in a larger hierarchical model) which are on a 0-1 scale, so there are posterior samples on ...
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### How do I calculate whether something is an independent risk factor?

I do not know what calculation/formula to use to show that something is an independent risk factor. E.g., in a cohort study: Group A (n=1000) - exposure to X - outcome exposed 70/1000 demonstrate Z ...
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### Computing event rates given RR + CI and total sample size in each treatment group

I am looking at some data for the risk of mortality in patients undergoing treatment A vs treatment B and I am given the total number of patients in each treatment arm and the relative risk + ...
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### How to interpret the output of predict.coxph?

After fitting a coxmodel it is possible to make predictions and retrieve the relative risk of new data. What I don't understand is how the relative risk is computed for an individual and what is it ...
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### Descriptive measures for 2x2 crosstabs with zeros

For 2x2 contingency tables I already know the RR (Relative Risk) and the OR (Odds Ratio). However none of these two is good dealing with empty cells in the table. | A | -A | B | n11 | n12 ...
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### Clinical trial question Confidence Interval

Data are collected in a clinical trial evaluating a new compound designed to improve wound healing in patients. The new compound is compared against a placebo. After treatment for 5 days with the new ...
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### Significant p-value and relative risk crossing 1

I am trying to convert results I am finding in scientific articles into relative risks so that I can compare studies in a meta analysis (if there is enough homogeneity in the studies). I came across ...
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### How are absolute risks estimated by the cox model?

According to my modest understanding, the cox model is all about estimating hazard ratios, relative measures of risk. However, it is possible (in R using e.g. the packages pec or peperr) to estimate ...
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### How do you explain the difference between relative risk and absolute risk?

The other day I had a consultation with an epidemiologist. She is an MD with a public health degree in epidemiology and has a lot of statistical savvy. She mentors her research fellows and residents ...
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### Where can one get real (health) actuarial/insurance probability data/distributions? [closed]

I'm researching some problems in the health/medical insurance sector and would like to use actual probability distributions (or current data) for doing some sort of risk analysis using simple ...
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### Poisson regression to estimate relative risk for binary outcomes

Brief Summary Why is it more common for logistic regression (with odds ratios) to be used in cohort studies with binary outcomes, as opposed to poisson regression (with relative risks)? Background ...
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### Visualizing change in risk ratio along with confidence limits

I want to graphically show the change in relative risk along with confidence limits over 17 years. Can I use a forest plot without meta-analysis because it will have the added advantage to tabulate ...
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### How to assess effect of intervention in one state versus another using annual case fatality rate?

I am a beginner in statistics with just basic knowledge. I have these data: cases, deaths and CFR (Case Fatality Rate-deaths per 100 cases) of a disease for 17 years (1994-2010) from 2 neighbouring ...
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### How to assess drug effects using annual death rate data?

I am planning a study to collect data of patients dying after brain infection versus number of cases for the next 5 years in 2 cities where they manage the disease with different drugs. Will a year ...
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### How to assess effect of intervention in one state versus another using annual death rate data?

I am a beginner in statistics. I have these unpublished data (cases and deaths) of a disease for 7 years (2004-2010) from 2 neighbouring states. The study was started in 2004. State 1 and State 2 ...
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### Prerequisite for conversion from odds ratio to relative risk to be valid

as question, since we can do the conversion from odds ratio (p1/q1)/(p2/q2) to relative risk (p1/(p1+q1))/(p2/(p2+q2)) fairly ...
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### Meta analysis on studies with 0-frequency cells

I am familiar with meta analysis and meta regression techniques (using the R package metafor from Viechtbauer), but I recently stumbled on a problem I can't easily ...
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### Inconsistency between Chi-sq and CI Estimation using Wald test

I am trying to calculate the relative risk for being tested as positive for people aged >25 or <=25, and here is the result. ...