Questions tagged [fishers-exact]

A hypothesis test for contingency tables.

Filter by
Sorted by
Tagged with
0
votes
0answers
28 views

Fisher's Exact Test and bonferroni correction in r

I try to find out whether there are significant differences in Categories between several groups. My data looks like: ...
0
votes
1answer
24 views

Interpreting infinite odds ratio and confidence interval from Fisher's test

I've performed a two-sided Fisher's exact test on the following data, and the results include Infinity for the upper confidence interval and odds ratio. Are these results erroneous, and if not how do ...
0
votes
0answers
16 views

Interpretation of chisquare and odds ratio

I am studying te association between variables and used the chisquare test and the odds ratio of fisher exact test. I would like to know the exactly interpretation that i can do. The main variable is ...
1
vote
3answers
47 views

Differences in Fisher exact test statistic

I am trying to perform Fisher test on the following matrix: 269 118 55 48 Several free websites including R fisher.test() ...
0
votes
0answers
33 views

Statistical test for differences in proportions, over-dispersed count data

I have a nxm contingency table where I have counts of elements divided by type. For example: I would like to know if the proportions of any of the columns are different (i.e., is the G1/G2 proportion ...
2
votes
1answer
30 views

Fisher Exact / Chi Squared Type I/II for low expected counts

For a 2x2 contingency table, I understand when the expected frequency is less than 5 that using Fisher's exact test is preferred (I recall reading it is done so that a multinomial is approximately ...
2
votes
2answers
36 views

Which analysis should I use

I am comparing data from two cohorts of patients that underwent a surgical procedure: Group 1 (2013-2015, n=157) and Group 2 (2016-2018, n=146). In both cohorts, I have patients that had survived and ...
2
votes
1answer
77 views

How does fisher.test calculate the confidence interval for the odds ratio in R?

The fisher.test function in base R by default returns a confidence interval for the odds ratio in a 2x2 contingency table. For example: ...
0
votes
1answer
15 views

Strange odds ratio (OR) derived from Fisher's test

I have frequency data for about 1000 genetic marker for two groups that I want to compare them between the two groups. I used Fisher’s test (in R) on the count data and got FDR and odds ratio (OR) for ...
0
votes
0answers
20 views

Are the classic assumptions for Chi 2 test still valid?

For a 2*2 table, I want to use Chi 2 test Are the classic assumptions (1# more than 80% of the contingency cells having expected values ­> 5, 2# no zero in the cells ) are still valid? Is existence of ...
1
vote
1answer
32 views

Is Fisher's exact test the most powerful test for 2x2 contingency table?

I don't find the powerfulness of Fisher's exact test on Wikipedia. Are there any results about the power of FET vs other methods on 2x2 contingency tables?
0
votes
0answers
20 views

Analysing contingency table with small samples

My question is about how to analyse very small samples on contingency tables. I have a contingency table with observation for 2 groups (first variable) answering questions with multiple choices (...
0
votes
1answer
36 views

What test to use when a chi-squared assumption is violated but my contingency table only has one row?

I have some data of lizard counts near rock piles of different types that I'm trying to analyse. There are three different types of rocks (control, design 1, and design 2) and I have a lizard count ...
1
vote
1answer
32 views

Does multiple pairwise fisher exact test need multiple testing correction?

I am aware of that multiple testing correction is needed when multiple hypothesis tests are simultaneously performed. However, I am a little confused by the word "simultaneously". Say I have ...
0
votes
0answers
21 views

Fisher's Exact Output Interpretation - Genstat

I'm working with Fisher's Exact Test in Genstat with data classified into a $2\times 2$ contingency table. The output I have got from performing this test it below, but I am unsure which $p$-value is ...
0
votes
0answers
26 views

Can I use a fisher's exact test for repeated measures?

I have a set of data working with embryos where I want to compare whether male carriers of a disease have a higher chance of outcome A than female carriers. My first thought was to do a fisher's ...
1
vote
1answer
86 views

Fisher's exact test: 95% CI or p-value

I have run proc freq to test association between two binary variables using the Fisher's exact test. However, the outputs seem contradict to each other as Two-sided Pr <= P 0.0355 whereas the OR ...
2
votes
1answer
257 views

Understanding “table margins”

I'm working on a statistics quiz and asked the following: What tables (with the same margins) would constitute stronger evidence of a gender bias effect in the calculation of the p-value using ...
0
votes
0answers
74 views

Chi Square and Fisher’s exact test with Monte Carlo

SPSS can’t calculate Exact test for 4x7 table of my data so I did it with Monte Carlo. The output is given below. Considering the rules of Chi-square, I should use Fisher’s $p$-value for the result of ...
0
votes
0answers
32 views

How IBM SPSS calculates exact p value for Pearson Chi-Square statistic?

Usually, I use Fisher's exact test p value when the sample size is small for Pearson chi-square test. Then I realized that IBM SPSS reports exact p values for all the tests (i.e. Pearson Chi-Square, ...
0
votes
1answer
25 views

co-occurence and mutual exclusivity of two events

I would like to compute co-occurence and mutual exclusivity for a set of events divided in two groups (A and B). Each event E_{x,y} represents if a mutation occurs ...
0
votes
2answers
26 views

Test statistical significance with small number - Fisher's exact test

Before the part of the question related to the title, here is some background: I'm build a model that tries to predict a binary outcome ($Y$), given a set of features. Some of this features are ...
0
votes
0answers
25 views

If I have less than 5 elements in a cell is there a way to use Chi Squared? [duplicate]

I have some data which has less than 5 elements in a cell, which would usually lead to fishers test being used instead. However, I'm unable to use fishers as there's not enough memory for it. chi ...
1
vote
1answer
81 views

Fisher exact test for mutation co-occurence

I've a dataset of 492 samples, for each sample I've information regarding if gene X has a germline mutation and a somatic mutation. I would like to test co-occurence of germline and somatic mutation ...
3
votes
2answers
837 views

Fisher exact test on 4 x 3 table, with low count?

I'm thinking about applying Fisher Exact Test for the following contingency table: ...
1
vote
0answers
33 views

Best test for 2xK contingency table with low cell counts and small overall sample size?

I am looking for the optimal test to use on a contingency table with 2 categorical variables (first variable has 2 levels, second has 4 variables). The cell counts can be as low as 1 or 2 and the ...
1
vote
1answer
395 views

Comparing proportions between multiple groups - Fisher's exact test

I have a simple dataset on reproductive success of a certain plant species. Reproductive success was defined as a proportion between number of flowers and number of fruits. We measured on 10 different ...
0
votes
1answer
109 views

Significant Fisher's exact test, post hoc analysis for subgroup comparisons?

I'm analysing 2 groups of patients with 2 different DISEASE_STAGES: MILD disease and MODERATE disease, as defined by a complex clinical diagnosis. The sample size is relatively small: a total of 80 ...
0
votes
1answer
79 views

fisher's exact test with values less than 1

I have a rxc contingency table that has values that are less than 1. For Example: ...
1
vote
0answers
32 views

Fisher's exact test with opposite direction of categories for two groups

I would like to analyze student performance under two teaching approaches for two classes. We predict that class 1 would outperform class 2 and ideally the performance between two classes should be ...
1
vote
2answers
489 views

Contingency table (2x4) - right test & confidence intervals

I have 2 categorical variables for each observation in my dataset: environment and behaviour. I'm trying to test association between them i.e. does the environment affect behaviour? The resulting ...
3
votes
2answers
472 views

Is a Fisher's Exact test in a 7x9 contingency table feasible?

I have a question regarding the use of SPSS (i.e. its capability) to execute a Fisher's Exact test for large, sparse RxC contingency tables. I would like to test whether or not a certain correlation ...
8
votes
1answer
203 views

When and how to avoid inappropriate use of Fisher's exact test

Could someone explain why Richard McElreath says Fisher's exact test is rarely used appropriately in his excellent Bayesian introduction book (Statistical Rethinking)? For reference, the context is ...
0
votes
0answers
49 views

Fisher's Exact Test: Compare 'A' vs 'Not-A'

I have data, which, as a table, is akin to this: ...
0
votes
0answers
72 views

Fisher's exact / Chi-squared tests with repeated/dependent observations

I have a dataset (structure explained below) for which I want to perform some tests on 2x2-tables. The data is generated from a (randomized) experiment, and structured as follows: I have n subjects, ...
1
vote
0answers
35 views

Fisher's or Bernards?

I work on animal behavior. I have a behavior data which is categorical/ nominal variable. It's in the form of a 4 by 4 contingency table with unfixed marginals hence unconditional. I am confused which ...
3
votes
1answer
244 views

Statistical testing for cohort analysis and retention: did I do this right?

A common problem in tech-startups is cohort analysis when A/B testing new app features: within a certain time period between two different dates, two different sets of users joining between those ...
2
votes
0answers
80 views

Probability of a contingency table with given marginals

In Fisher's exact test we consider all contingency tables $(n_{ij})_{i,j=0,1}$ consistent with given marginals $(n_{0.},n_{1.},n_{.0},n_{.1})$, where $\sum_i n_{i.}=\sum_j n_{.j}=N$. Each table has ...
0
votes
1answer
101 views

Fisher test of a Likert survey

For my thesis i have to find out if there is any statistical correlation between a Traditional+Experimental teaching method (compared to a merely traditional one) and a highier level of understanding ...
0
votes
0answers
37 views

Triangle-shaped contigency tables

Suppose there are random values $\xi,\eta \in \{0,1,2\}.$ I have two samples by which I can build following contigency table: \begin{array}{|c|c|c|c|} \hline \eta \text{\\} \xi& 0 & 1 & ...
1
vote
1answer
41 views

A situation where to consider row totals in a $2\times 2$ contingency table fixed or not?

In a prospective study, we draw a sample of size 100 where two sttributes A and B were present. Our goal is to assess whether ...
1
vote
1answer
119 views

Combining multiple contingency tables

I have images that are evaluated by different experts. Basically, each expert look at the same pictures and saying whether a feature in the image exists or not. We have some images from diseased and ...
7
votes
1answer
800 views

McNemar or Fisher exact test for propensity score matched data?

I want to analyze some propensity score matched data. In the literature McNemar test is usually used, since the data is "paired". However matching is not pairing in the common sense. Would it be ...
1
vote
0answers
189 views

How to use Fisher's exact test to show the significance of “the proportions at one variable are the SAME for different values of the second variable”?

We are working on a bioinformatics problem. We have a collection (say $U$) of kmers or small substrings of length $k$ of some set of sequences. We have two different experiments. Only a subset of ...
0
votes
1answer
57 views

Can Fisher's Exact have H0 = one tail, and HA = “no difference” + the other tail?

There are two populations called Traditional and Experimental, and a rate is calculated for each. Performance for the Experimental group is considered favorable if the rate is EQUAL TO or LOWER THAN ...
0
votes
1answer
78 views

small sample size with Likert data

I have 5 point Likert scale answers to questions and I want to compare the results for 2 practice types. I have only 17 respondents from one type so I believe my best approach is the Fisher exact ...
0
votes
1answer
210 views

Fisher Exact and Z-score for test for two proportions

I am wondering why/when would I be indicated to use the Fisher Exact Test as Opposed to calculating a Z-score for a test for two proportions? I am assessing some proportions, and my understanding is ...
1
vote
1answer
118 views

Nominal and non-dichotomous variables

I am having problems analysing baseline data for my study population. My variables are erection dysfunction severity (mild, moderate and severe) and type of erection dysfunction (organic ED and ...
2
votes
0answers
133 views

Have I chosen appropriate statistical tests to analyze my 2x2 and two-by-k tables?

I am analyzing a number of 2x2 and two-by-k tables in a cross-sectional study using Pearson χ2 tests and Fisher’s exact test (or the Fisher-Freeman-Halton exact test) “as appropriate.” Here is a ...
-1
votes
1answer
81 views

Fisher Exact Test Question

I have: Group A using T method and Group B using E method. Out of a total of 36 possible problem issues. Group A using T method finds = 26 issues. Group B using E method finds = 28 issues. How do ...