Questions tagged [exact-test]

Statistical tests where the sampling distribution is necessarily exactly correct & not an approximation based on assumptions &/or large sample theory.

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4
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2answers
47 views

Single sample t-test variance assumptions for non-normal data

So I understand that a key assumption behind the single sample t-test is that the sample mean is normally distributed. This is true when the data themselves are normally distributed, and it is ...
7
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2answers
105 views

Paired vs independent t-test for A/B test with underlying trends

There is a metric which has a natural cyclic pattern. We want to measure the effect on this metric through a A/B test. Examples: Metric is daily revenue of ice-cream trucks which is low during ...
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0answers
10 views

Fixed/unfixed maginals in case/control studies on pre-existing data?

I am performing analyses on a wide variety of existing datasets (taken from GEO) with case/control status. I want to do exact tests on a 2x2 contingency table and am unsure if I should use Barnard's ...
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1answer
50 views

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 ...
0
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1answer
12 views

Check if multiple percentage are significant

I have 3 measurements of a very skew distribution, depending on three different technique. In general, I can do thousands of test and the result is either "fail" or "success", being the "fail" far ...
3
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1answer
46 views

Exact distribution of number of transitions in a binary vector of length $n$

I am trying to derive an analytic solution for the exact distribution of the number of transitions in a binary vector of length $n$ conditional on the observed number of $1$'s and $0$'s and under the ...
3
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1answer
234 views

Confidence interval for quantiles: distribution-free, asymptotic and assuming a normal distribution

An acquaintance of mine has been using this wrong inference formula for years: given a i.i.d. sample $\mathbf{X}={X_1,\dots,X_N}$ for a continuous RV $X$, sample mean $\bar{X}=\frac{\sum X_i}{N}$ ...
3
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1answer
52 views

Examples for exact tests which are not permutation tests

Wikipedia states (without citation): Sometimes permutation test is used as a synonym for exact test, but although all permutation tests are exact tests, not all exact tests are permutation tests. ...
1
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1answer
31 views

Number of all sample divisions in permutation test

I have a question with regard to the number of permutations in a permutation test. Assume I want to do a two group independent t-test. In the permutation variant of the t-test, I would repeatedly ...
1
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1answer
186 views

How does Normal approximation work when ties exist for Wilcoxon Signed rank test?

I ran wilcox.test() in R (outcome variable was a test score and the data was paired samples) and got a warning message saying that it cannot generate a p-value for tied values. I saw the R document ...
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0answers
41 views

How to perform an exact test of Chi-square for a single-dimension data in R?

I have a data frame like this: > fr.t.r A B C D E Freq 13 3 0 0 0 and I would like to do a Chi-square test to find out if the ...
0
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1answer
592 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
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0answers
47 views

when an exact binomial confidence interval should be used?

Is exact binomial confidence interval only appropriate for extremely rare events or extremely frequent events? If so, what are the rule of thumb for the definitions of extremely rare (<0.01?) And ...
1
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1answer
232 views

Exact MCMC Logistic Regression Output

I am having trouble interpreting the output of an MCMC Logistic Regression run using R from the MCMCpack. Unfortunately I have had very little luck in finding sources on the web. I am assuming that ...
1
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0answers
82 views

LRT and $\text{Uniform}(0, \theta)$

We have one observation of variable $X$ that is distributed uniformly on $[0, \theta]$. Null hypothesis is $H_0 \colon \theta = 1$ and alternative hypothesis is $H_1 \colon \theta = 2$. What is the ...
6
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2answers
156 views

Drawing conclusions of several inferences with the same data in one study

In a sample size of 100, we identified the existence of two attributes A and B. Our goal is to assess whether there is any ...
3
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1answer
1k views

One-sided McNemar's test

In R, the function mcnemar.test has the following example: ...
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0answers
77 views

Barnard's exact tests - papers?

I am currently writing some essay for the university in which I should give a quick overview over exact methods for independence testing on contingency tables, after writing down the stuff for Fisher'...
1
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0answers
241 views

Boschloo's exact test

I have following data in R: d1 <- matrix(c(24,2,63,11),2,2, dimnames=list(X=c("present", "absent"),Y=c("present", "absent"))) I want to test ...
5
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1answer
752 views

z-test for one population proportion hypothesis with a small sample size

I have asked a "yes/no" question to a small group of people (n = 22). From the 22, 14 answered "yes" and 8 answered "no". I'd like to find out, with 90% confidence, if the majority of my population (> ...
0
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1answer
335 views

Sample size determination for comparing two independent samples with regards to several continuous variables

I am interested in calculating the required sample size to perform several statistical tests on the same sample. More precisely, this is the situation: There are two groups of individuals, A and B, ...
5
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0answers
150 views

Exact Null Distribution with Ties

I am interested in deriving exact null distributions for small-sample test statistics with non-trivial ties. Not fundamentally continuous variables that happen to have a few repeated values, but ...
3
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0answers
547 views

pre-post testing: paired nominal data with more than 2 categories

I have two groups of students who answered a question on the pre-survey about their savings behavior, i.e. choose one answer a/b/c/e/d/f: (a) Save the same amount each week, (b) Save varied amount ...
1
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1answer
164 views

how we do student T-Test?

In my data water is control and gibberellin is positive control. We want do find the activity of steviol against water and gibberellin. How we do student T-Test?. My data of height of plant in cm is ...
2
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0answers
152 views

Covariates in a case control study

I am doing a retrospective analysis on a study has has cases and controls. I am looking to see if there is an association with death, using exact logistic regression. I am confused on whether I need ...
3
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0answers
3k views

Threshold for and Variations of Exact logistic regression

According to this UCLA tutorial exact logistic regression (elrm::elrm in R) should be prefered to the logistic regression ...
2
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1answer
398 views

Exact multinomial goodness-of-fit test as a normality test

We have a practical real-life problem in an open source Linux related project. And I would like to hear an expert review/opinion about the way we are trying to solve this problem. It's been more than ...
5
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1answer
2k views

How do you know if your confidence interval is exact or approximate?

I would like to know the rules between the two, and know how you know the differences.
1
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1answer
1k views

What is the minimum sample size for an exact binomial test of goodness of fit (two-tailed)?

I am doing a two tailed exact binomial goodness of fit test, see, e.g., here. I am looking for something similar as for Chi-square tests, which, as a rule of thumb, require a frequency of 5 for each ...
4
votes
1answer
977 views

Exact test for m x n contingency table conditional (i.e. fixed by design) on one margin

I have a $m \times n$ contingency table (with $m, n > 2)$ . The experiment yields ~15% cells with expected frequencies lower 5 and also zero counts in the empirical data. The prerequisite for the ...
3
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0answers
69 views

Test of strict difference in independent binomial probabilities

Suppose $X,Y$ are two independent binomial random variables with parameters $n_1,p_1$ and $n_2,p_2$ respectively. Suppose one wanted to test the hypothesis $p_1>p_2$. Conditional on $X+Y=s$, ...
3
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1answer
402 views

Non-parametric, repeated measures two-sample test with small sample size

My data consists in two samples relative to the expression of a given gene, with 4 replications in both samples. I am interested in testing whether the two samples come from the same population, ...
2
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0answers
173 views

Questions about non-standard test statistic for difference of two population proportions

Background I'm considering the number of observed 'successes' $x_1$ and $x_2$ from $n_1$ and $n_2$ independent trials respectively. These counts can be considered realisations of random variables $...
9
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3answers
553 views

Test to distinguish periodic from almost periodic data

Suppose I have some unknown function $f$ with domain $ℝ$, which I know to fulfill some reasonable conditions like continuity. I know the exact values of $f$ (because the data comes from a simulation) ...
1
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2answers
203 views

An exact paired perm.test is returning a p-value of 0 for large sample sizes

I'm trying to find the p-value from an exact paired permutation test. For small samples it works fine: ...
4
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1answer
984 views

Proper analyses for 2x2 contingency tables

So I have multiple questions about the different types of analyses that can be used on a 2x2 contingency table and when different analyses should be used. To open, I'll note that this stems from my ...
4
votes
2answers
1k views

Is the binomial sign test really the exact McNemar test?

I am calculating two different $p$ values for the McNemar test and what I believe is the corresponding exact test, even for combined counts larger than 25. Take, for example the contingency table <...
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0answers
37 views

exact test on proportion: confidence intervals vs p value [duplicate]

I have the following 2x2 table NO YES 9690 5 LOW 26354 39 HIGH I want to plot the proportions and ...
0
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0answers
435 views

Exact p-value for any nonparametric test

After having found the R-package coin, I have a question. For example, to get an exact p-value, I could use the function ...
1
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1answer
410 views

Exact probability and asymptotic approximation

From Wikipedia A large amount of computing resources is required to compute exact probabilities for the Kruskal-Wallis test. Existing software only provides exact probabilities for sample sizes ...