Questions tagged [fishers-exact-test]

A hypothesis test for contingency tables.

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Establish confidence / error for multiple contingency tables with dynamic outcomes

In a task, a participant sees two types of prompts, 1 and 2. The participant might answer A or B. The participant might give an answer that cannot be coded as A or B, we treat these as missing data. ...
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28 views

Use of Chi-Square test of independence / Fisher Exact Test?

One of my research hypotheses is that individuals from Southeast Asia who are ethnically Chinese are more likely to experience racially motivated hate crimes than their counterparts from other ethnic ...
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Interpreting post hoc multiple comparisons test?

I have a conducted a Fisher's exact test with Monte Carlo simulation which resulted in a significant p value. My row variable, which is the # of people, has 4 levels (0, 1-50, 51-100, 101-150) and my ...
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33 views

Post hoc test for Fisher's exact test (larger than 2x2)?

I have 2 categorical variables: Var1 - 3 levels, Var2- 5 levels (i.e., table is bigger than 2x2). I'm using SAS, and since I have multiple cells <5, I have run a Fisher's exact test with Monte ...
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Sample size for binary outcome with rare events

I want to compute the sample size to compare two groups for a binary outcome where we expect rare events. I will do an example with R. Assume the following expected probabilities of observing an event ...
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Comparing multiple sample proportions between two groups

Hi all and thanks for taking the time to read this question. I'll try to be as clear as possible! The data: I have one sample of patients which was divided in two groups based on a binary variable for ...
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Multiple, One Category Chi Square tests vs Single, multiple category Chi Square test [duplicate]

my statistical skills are rather basic so was hoping I could get some insight. Let's say I'm analyzing the demographics of two population groups for variables such as 1. tobacco use, 2. alcohol use, ...
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Can the Fisher exact test be used to get a confidence interval for the efficiency of a vaccine (risk ratio or relative risk)?

Consider the Pfizer vaccine for COVID-19. The data from the phase 3 trials shows that they had 21720 people in the vaccinated group and 21728 people in the control group: ...
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How to compare patient groups in cohorts containing different distributions and subtypes?

I have performed targeted sequencing on a panel of genes resulting in variant data for a cohort consisting of patients with different cancer diagnoses. These same genes have been analyzed in other ...
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Are the sum values 'No' and 'Not informed' in the Odds Ratio analysis correct? See the example

In a hypothetical study I am trying to assess whether the presence of allergy is a risk factor for the presence of any virus. For this purpose, a questionnaire was applied on which many individuals ...
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Are the data grouped by different drug doses graded data or disordered data?

I have a set of data, the structure is as follows: 5mg 10mg 15mg 20mg Survive 15 22 18 24 death 3 2 3 2 I divided the patients into 4 ...
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For the confidence interval of median using the binomial distribution why is it called exact and how does it differ from the naive loop-based method?

When I searched across documentation of various statistical packages, I noticed that the confidence interval for median based on either the binomial or beta distribution is called exact. For example: <...
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Algorithm to compute p-value of Fisher's exact test based Monte Carlo (bootstrap) simulation

I am looking for code to compute the 1- and 2-sided p-value for Fisher's Exact test for 2x2 tables based on Monte Carlo (bootstrap simulations). For larger 2x2 crosstabulation tables, the exact p-...
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Fisher's Exact Test for many 2x2 data sets

I'm trying to find an appropriate test or method to determine if the presence of a binary condition causes a separate binary result, given lots of situations (data points) of the 2x2 input/output ...
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Is Pearson's chi-squared test of independence conditional on marginal distributions?

The Wikipedia page on Pearson's chi-squared test states that a difference to Fisher's exact test is that the latter makes the "assumption of fixed marginal distributions". I assume that ...
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How to interpret significant likelihood ratio and insignificant Chi-square tests?

To analyze frequencies in a 2x2 table, I ran a statistical test procedure using SPSS. It returned a p less than .05 for the likelihood Ratio but greater than .05 for Chi-Square and Fisher Exact Test (...
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Statistical test for comparison of counts for 2 groups where requirements for Chi-Square test are not met

I would like to compare overall codon counts in the yeast genome with codon counts from an individual sequence. The totals for the 2 groups are not the same. I cannot use a chi-square test, since when ...
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Analysis of Danish mask study data by Nassim Nicholas Taleb (binomial GLM with complete separation)

Recently, Nassim Nicholas Taleb made this post about the recent Danish mask study, a randomized controlled trial which concluded that the proportions of newly diagnosed coronavirus infections was not ...
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Comparing win loss records or test results for statistical difference

I was reviewing some game statistics of wins and losses and was wondering what is the best approach to differentiate between how likely a person or team who had come in first is statistically that ...
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105 views

Test if two averages of two binomial distributions are statistically significant to one another

First, this may be a duplicate of: statistical significance I'm unsure if that post covers my exact situation. If so, just mark this as a duplicate. Let's say I have a list of 100k potential clients ...
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Fisher's exact test on Frequency of Occurrence data

I am working with diet data of chicks from a single colony from multiple seasons. The data consists of actual counts and frequency of occurrence (%) of 4 prey groups from 8 seasons extracted from diet ...
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102 views

Help with a 2x3 contingency table significance test

MD here completely new to doing my own statistics In a study I'm currently working on, I have three groups that I am assessing for a various categorical Yes/No Variables, for example: Without ...
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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 OR overlaps 1? My understanding ...
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outage frequency analysis

I have several outage data points. Each outage has a time category (TP1 - TP3 - one could argue this is an ordinal variable) and week day. The rolled up (artificial) frequencies data looks as follows: ...
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Random distribution which statistical method

After K-means, I am iterating over many files consists of tables, mostly are 3X3. Some of them with "0" elements inside cells but most of them aren't. I read that chi2_contingencycouldn't be ...
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Choice of covariate under Independent Hypothesis Weighting (IHW)

After reading this survey of methods for controlling FDR and considering my problem at hand (https://genomebiology.biomedcentral.com/articles/10.1186/s13059-019-1716-1), IHW seems like a good choice. ...
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Best method to analyse multiple 2x2 contingency tables of a small sample?

I already looked around quite a bit but didn't find answers (I understood), so I apologise if this question should be a duplicate. I'm analysing a small cohort (n=15) of people with some observed ...
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106 views

Connection between Bayesian A/B testing and Fisher's exact test (specific example on Hydroxychloroquine trials)

I understand that there are multiple comparisons floating around between Fisher's Exact Test and Bayesian A/B Testing, here's an example. While I do understand these are fundamentally making different ...
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Power of Fisher test vs chi squared

Consider an $m \times n$ contingency table and test of independence. Suppose the expected counts are such that chi-squared test is not recommended (close to zero in some cells), as it becomes pretty ...
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Which test fits the best here? (oncogenic signalling pathways)

I have a list of patients in rows and oncogenic signalling pathways in columns of two independent matrices One for responders to a drug one for non-responders to the same drugs If a patient gets ...
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Chi squared test questions

As part of a small study, I've have put together a table with results from a population of individuals stratified by age. For each line, I would like to perform a comparison between a variable and the ...
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101 views

Why am I getting p=1 in Fisher's exact test?

I have 8 IV and 1 DV, they are all dichotomous and categorical data, so I am using Cross-tabulation Chi-square test. So 8 tests conducted. All test have at least one expected count less than 5. So I ...
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Comparing multiple distinct proportions between two groups

I have two groups (group 1: $n=100$, and group 2: $n=200$), and multiple proportions for each group (where the number represents the proportion of individuals in the group with each disease). Example: ...
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Does it have any meaning to compute the $\chi^2$ and the exact Fisher test on big contingency tables

I have several datasets containing integers. I want to perform a bivariate analysis between a specific subset of variables. However, some of them have a lot of modalities. Is computing a $\chi^2$ ...
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How to deal with zero cells in 2 x 2 tables, using R

I am trying to look at the relationship between two nominal variables, using R. However, I am not certain how to deal with cases where a 2 x 2 contingency table has one or more zero cells, as shown ...
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On power of solving Lady Tasting Tea?

I've learned that the solution for the lady tasting tea experiment is the Fisher's exact test. Is it the most powerful test for solving this problem? If there are other tests, how do they compare in ...
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Interpretation of Fisher's exact test confidence interval

I am having difficulties with the interpretation of Fisher's exact test confidence interval. I have a contingency table with some numbers below 5 table data, so I perform Fisher's exact test: ...
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What statistical test should be used to compare groups when the assumption of independence is violated?

I would like to test if there are statistically significant differences between three groups (defined by an outcome measurement) for some categorical and continous variables, respectively. Normality ...
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How can I separate the abundance factor of the incidence results?

I must calculate the incidence values for Watermelon Mosaic Virus in different seasons within of habitat. This incidence data comes from infection detection of some plant sampled in different habitats ...
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Calculate group with highest defective rate

I have data on several types of machines, each with a different rate of failure. I have samples of failures/non-failures for each machine type. The samples are small relative to the population range ...
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Two sample test of independent proportions with weighted data?

In analysis of survey data, response data may often be weighted to reflect the sampling procedure or relative importance of the respondents. For instance, a consumer survey may sample 50 respondents ...
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300 views

Fisher's exact test (one-sided, greater) gives p-value = 1

I have a contingency table that looks like this ...
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What is the value of an infinite odds ratios with non-signification p-value?

I have a contingency table as follows: Tumour Healthy Pos Neg Pos 4 0 Neg 2 3 I ran Fisher's exact test to get the odds ratio (using R) and ...
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Can exact tests compare groups from case-cohort studies?

I have reviewed several helpful threads most related to my question and many thanks to the authors. The first thread suggests odds ratio is valid for cohort studies, but risk ratios or hazard ratios ...
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Statistical test to show if there is a difference between A and B (count data)

I conducted 20 tests (in parallel) where there was a choice between A and B and after a defined period of time, I counted the number of individuals that chose A or B (count for A and B is always ...
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Comparing responses between groups and conditions

I have a group of subjects that were tested under 2 visual stimuli. Each stimuli was presented in 2 directions (the stimulus is a flow of objects, once left to right and then right to left). And the ...
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1answer
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How can I do fishers exact test if only frequency is available not the count?

I want to compare two allele frequencies from two populations. I use Fisher's exact test for this. But I don't have the actual count of the alleles but just frequency. For eg: Frequency of Population(...
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Confirm that an eventual over-representation in a sample is statistical significant

I need opinions on this one, so any thought you can contribute will be highly appreciated. My population is an entire set of customers, my sample is all the customers to whom something specific, which ...
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Testing the difference in sensitivities between two lab tests - with part overlapping populations

I have two rapid diagnostic tests for which I test their sensitivity (+/-) in detecting cases against the gold standard (ELISA, also +/-). I now want to test whether the tests perform significantly ...

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