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Questions tagged [odds-ratio]

A measure of association between two binary variables equal to the odds of a 'positive' outcome in 1 variable divided by the odds in the other. The OR ranges (0, infinity). It has a strong connection to logistic regression.

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Interpretation of simple predictions to odds ratios in logistic regression

I'm somewhat new to using logistic regression, and a bit confused by a discrepancy between my interpretations of the following values which I thought would be the same: exponentiated beta values ...
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Why do my p-values differ between logistic regression output, chi-squared test, and the confidence interval for the OR?

I have built a logistic regression where the outcome variable is being cured after receiving treatment (Cure vs. No Cure). All ...
SniperBro2000's user avatar
27 votes
1 answer
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Help me understand adjusted odds ratio in logistic regression

I've been having a hard time trying to understand the use of logistic regression in a paper. The paper available here uses logistic regression to predict probability of complications during cataract ...
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50 votes
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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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19 votes
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Negative coefficient in ordered logistic regression

Suppose we have the ordinal response $y:\{\text{Bad, Neutral, Good}\} \rightarrow \{1,2,3\}$ and a set of variables $X:=[x_1,x_2,x_3]$ that we think will explain $y$. We then do an ordered logistic ...
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14 votes
1 answer
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How to conduct a meta-analysis on studies that report results variously as odds ratios, hazards ratios, or rate ratios?

I'm doing a meta-analysis of some studies that report results variously as odds ratios, hazards ratios or rate ratios (all with confidence intervals). Is there any way to combine these together/...
Mark Greenaway's user avatar
59 votes
7 answers
208k views

Logistic Regression in R (Odds Ratio)

I'm trying to undertake a logistic regression analysis in R. I have attended courses covering this material using STATA. I am finding it very difficult to replicate ...
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4 answers
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Why do odds ratios from formula and R's fisher.test differ? Which one should one choose?

In the following example ...
winerd's user avatar
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16 votes
2 answers
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How do I calculate the standard deviation of the log-odds?

I have in my notes that the standard deviation of log odds is given by the $$\sqrt{(1/a + 1/b + 1/c + 1/d)}$$ I know that the derivation of this requires the Delta Method, but I'm not familiar with ...
Parseltongue's user avatar
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16 votes
3 answers
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Different ways to produce a confidence interval for odds ratio from logistic regression

I am studying how to construct a 95% confidence interval for odds ratio from the coefficients obtained in the logistic regression. So, considering the logistic regression model, $$ \log\left(\frac{p}{...
Márcio Augusto Diniz's user avatar
15 votes
1 answer
1k views

Is meta-analysis of odds ratios essentially hopeless?

In a recent paper Norton et al. (2018)$^{[2]}$ state that Different odds ratios from the same study cannot be compared when the statistical models that result in odds ratio estimates have different ...
COOLSerdash's user avatar
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9 votes
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Converting odds ratios to Cohen's d for meta analysis

I'm conducting a meta-analysis largely on mean differences data, however I have several articles that report only an odds ratio, N, p value, and confidence interval, and I need to convert this ...
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How to interpret odds ratio?

Suppose we have a baseline exposure group and 2 other exposure groups for a case control study. Suppose the odds ratio for the first exposure is $1.5$ and the odds ratio for the second exposure is $1....
guestguy's user avatar
18 votes
2 answers
22k views

Calculating risk ratio using odds ratio from logistic regression coefficient

I have a binary logistic regression with just one binary fixed factor predictor. The reason I don't do it as a Chi square or Fisher's exact test is that I also have a number of random factors (there ...
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14 votes
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Is there any functional difference between an odds ratio and hazard ratio?

In logistic regression, an odds ratio of 2 means that the event is 2 time more probable given a one-unit increase in the predictor. In Cox regression, a hazard ratio of 2 means the event will occur ...
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6 votes
3 answers
34k views

How to calculate SE of an odds ratio

If one is calculating odds ratio with a,b,c and d counts, I believe variance of log(OR) is given by var_log_OR = (1/a + 1/b + 1/c + 1/d) Hence one can calculate ...
rnso's user avatar
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5 votes
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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 (...
Vic's user avatar
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3 votes
1 answer
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Why not always present logistic regression estimates in the response scale (probablity)?

There's a lot of discussion in epidemiology around the relative merits of odds ratios vs risk ratios. Proponents of the former cite the mathematical qualities of odds (not constrained to be between 0 ...
Lachlan's user avatar
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17 votes
4 answers
16k views

What is the distribution of OR (odds ratio)?

I have a bunch of articles presenting "OR" with a- 95% CI (confidence intervals). I want to estimate from the articles the P value for the observed OR. For that, I need an assumption regarding the ...
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12 votes
3 answers
83k views

How to calculate Odds ratio and 95% confidence interval for logistic regression for the following data?

I have the following data from a Research paper: S1 : n = 30 / Rest : n = 66 SH 11 / 8 For this to calculate p-value I have done it like following: <...
stack_learner's user avatar
11 votes
2 answers
12k views

Odds and odds ratios in logistic regression

I am having difficulties understanding one logistic regression explanation. The logistic regression is between temperature and fish which die or do not die. The slope of a logistic regression is 1....
Eddie's user avatar
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10 votes
2 answers
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Does the "divide by 4 rule" give the upper bound marginal effect?

In the logisitic regression chapter of "Data Analysis Using Regression and Multilevel/Hierarchical Models" by Gelman and Hill, The "Divide by 4" rule is presented to approximate average marginal ...
Michael Webb's user avatar
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9 votes
1 answer
18k views

Manually calculating logistic regression coefficient

I am taking this short example from wiki:https://en.wikipedia.org/wiki/Logistic_regression ...
user2542275's user avatar
7 votes
1 answer
2k views

Why is the Bayes factor sometimes considered more important than the Posterior Odds?

To the best of my knowledge, the posterior odds satisfies the equation: $$(\text{posterior odds}) = (\text{Bayes factor}) \times (\text{prior odds}) $$ This is a simple consequence of Bayes' rule. The ...
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How can I explain proportional odds models to a layman?

I'm writing an interdisciplinary research paper and I'm having some troubles in clearly explaining my findings. In particular, I applied a proportional odds model with one regressor $x$ and three ...
stochazesthai's user avatar
7 votes
3 answers
2k views

Explaining Odds Ratio and Relative Risk to the statistically challenged

I'm peer-reviewing a manuscript for a psychology journal in which I believe the authors have mixed up odds-ratio and risk-ratio. They are being so stubborn in their insistence that they have not mixed ...
Amorphia's user avatar
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1 answer
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Does confidence interval for odds ratio assume log-normal distribution?

The formula floating around for calculating 95% confidence interval of an odds ratio is: e^(log(OR) ± 1.96 x sqrt(1/a + 1/b + 1/c + 1/d)) Does one need to ...
Ray Zhang's user avatar
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6 votes
2 answers
1k views

How can I compute a log odds ratio for a within-subject design that could be meta-analyzed with log odds ratios from between-subject designs?

Background and Problem I have a question concerning a meta-analysis combining effects from between- and within-subject designs using log-odds ratios (OR) as the metric of interest. I am familiar with ...
jmfawcet's user avatar
  • 432
6 votes
1 answer
418 views

Why odds ratio in logistic regression

I'm a bit confused about odds ratio in logistic regression (LR). In a logistic regression textbook (pdf), it says that the odds ratio (OR) is $OR = \exp(\beta_0 + \beta_1X)$. But, I don't understand ...
user1480478's user avatar
5 votes
1 answer
1k views

Why is my Fisher's test "significant" but odds ratio overlaps 1?

Given a contingency table of the following rare event, why does my Fisher's exact test produce a "significant value" (i.e., < 0.05) but also show that the confidence interval for OR ...
Dylan Russell's user avatar
4 votes
1 answer
3k views

Restricted Cubic Spline Function Summary Intepretation

I am trying to incorporate spline transformation into my logistic regression and finally piece together the following (working) R code (pls see it below). However, I have no idea how to interpret this ...
R Beginner's user avatar
4 votes
3 answers
464 views

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 ...
DrWho's user avatar
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3 votes
3 answers
1k 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 ...
user149054's user avatar
3 votes
2 answers
485 views

Odds ratio and relative risk

I'm trying to understand how the odds ratio can approximate the relative risk under the rare disease assumption. I'm given the relative risk for disease $B$ and risk factor $A$ is 2 and that 20% of ...
statian's user avatar
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3 votes
1 answer
6k views

Odds ratio for poisson regression

Can I compute Odds ratio coefficients and their 95% CI from a Poisson regression (GLM) using the exp function? I have an ordinal dependent variable (i.e., a GS of a scale) and some independent ...
Valentina's user avatar
2 votes
3 answers
5k views

Logistic regression coefficient too high - cannot interpret odds ratio

Question of the day: I'm running a logistic regression (results below), and I come across a coefficient that is insanely large (in absolute terms). Usually, we don't care about things like that ...
Kirill Eremenko's user avatar
2 votes
1 answer
4k views

Describing Results from Logistic Regression with Restricted Cubic Splines Using rms in R

Updated I have been developing a logistic regression model based on retrospective data from a national trauma database of head injury in the UK. The key outcome is 30 day mortality (denoted as "...
Dan Fountain's user avatar
1 vote
0 answers
203 views

Do small odds ratios observed at multiple time points equate to a large odds ratio when averaged across time points?

I am testing the relative odds of two groups, placebo vs active treatment, guessing that they received active treatment. These guesses were made at four time points, 4, 8, 12, and 24 weeks into a ...
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1 vote
2 answers
2k views

Odds ratio meta analysis with no control group

Is it possible to conduct a meta-analysis odds ratio with just an experimental group (no control)? I am looking at several studies that have an experimental group, with a response rate equal to the ...
statsguyz's user avatar
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11 votes
2 answers
4k views

Odds ratio vs probability ratio

An odds is the ratio of the probability of an event to its complement: $$\text{odds}(X) = \frac{P(X)}{1-P(X)}$$ An odds ratio (OR) is the ratio of the odds of an event in one group (say, $A$) versus ...
Alexis's user avatar
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10 votes
2 answers
3k views

Interpreting logistic regression coefficients with a regularization term

I understand the coefficients of a logistic equation can be interpreted as odd ratio. If a regularization term is added to control for over-fitting, how does this change the interpretation of the ...
Jim T's user avatar
  • 101
9 votes
4 answers
12k views

How to calculate confidence intervals for pooled odd ratios in meta-analysis?

I have two datasets from genome-wide association studies. The only information available are the odd ratios and their confidence intervals (95%) for each genotyped SNP. My want to generate a forest ...
BIBB's user avatar
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9 votes
1 answer
39k views

Relation between logistic regression coefficient and odds ratio in JMP

From the output of a logistic regression in JMP, I read about two binary variables: Var1 estimate -0.1007384 Var2 estimate 0.21528927 and then ...
glassy's user avatar
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7 votes
3 answers
3k views

Log odds ratio - what happens if linearity fails?

I haven't found much info on this by googling so i thought maybe someone where has some answers for me. When it comes to binary logistic regression the model assumes that the log odds ratio has a ...
Janono's user avatar
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7 votes
5 answers
15k views

How to convert sport odds into percentage?

I am wondering how to convert sport odds to the percentage format. There's this example: ...
user984621's user avatar
7 votes
2 answers
1k views

Understanding Odds Ratios in Logistic Regression

I'm trying to understand how to interpret log odds ratios in logistic regression. Let's say I have the following output: ...
ATMathew's user avatar
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6 votes
1 answer
5k views

Converting Adjusted Odds Ratios to its RR counterpart

I am doing a meta-analysis of studies which reported their estimates sometimes as OR and sometimes as RR. I wanted to convert the OR to RR, so that I can pool them together. I know that I can use this ...
Amirhossein Modabbernia's user avatar
6 votes
3 answers
4k views

Interpreting odds ratios

I have the following set of results for one of the factors (birth weight) with different levels and their corresponding Odds ratios for survival. I am using the first level (<1.25) as the reference ...
baz's user avatar
  • 157
5 votes
1 answer
8k views

The effect of skewed continuous predictors in a binary logistic regression model

I am analyzing data with a binary outcome and a variety of continuous and categorical (including dichotomous) predictor variables. My approach is to perform a binary logistic regression and to treat ...
Ariel's user avatar
  • 518
5 votes
2 answers
14k views

How do I interpret the odds ratio of an interaction term in Conditional Logistic Regression?

I am wondering what the correct interpretation of the odds ratio of an interaction term in conditional logistic regression is. Let's say there are two independent variables A and B, as well as an ...
Statphil's user avatar