# Tagged Questions

22 views

### Difference estimate & confidence intervals for $\chi^2$ test between 2 proportions

I am using a chi-sq test between two proportions (http://statistic-on-air.blogspot.com/2009/07/comparison-of-two-proportions.html). I am using this over the z-test for proportions because I do not ...
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### Power of $\chi^2$ tests for homogeneity and independence

I recently studied these topics and I was wondering what their power is. My opinion is that since we are relying on an approximate chi-square distribution it cannot be much and so we have to be extra ...
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### Using $\chi^2$ or Fisher's exact test with low expected counts

Let's say I have 7 urns filled with random numbers of colourful marbles. An example dataset is as below: ...
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### How to test for randomness in bins with small N?

I observe a series of crime incidents linked by modus operandi or some other peculiar characteristic of the crime (e.g. cutting catalytic converters from underneath vehicles). I would like to know if ...
53 views

### Generic test for unimodality given sample

Are there any generic tests to validate if a given sample follows a unimodal distribution, like a Gaussian, Cauchy, Student's t or a chi-square?
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### Advice on comparing methods of generating random vectors

I'm researching a method for sampling uniformly from an $n$-dimensional shape, for which conventional rejection sampling may be too slow. I am generating 1,000 points using each method, and wish to ...
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### Stouffer's Z-score method: what if we sum Z^2 instead of Z?

I am performing $N$ independent statistical tests with the same null hypothesis, and would like to combine the results into one p-value. After some googling it seems to me that there are two ...
232 views

### Which test to check statistical relationship betwen paired/unpaired data?

I have data that is in-between of "independent samples" and "paired samples". About 50% to 70% of observations are matched (paired) and the rest miss a pair. Which test should I use - chi-square ...
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### How to get the expected counts when computing a chi-squared test?

I just have 1500 data points in excel. However, I want to do a chi squared test to prove if the data is normaly distributed. My question is: How to calculate the expected range for such a large data ...
469 views

### How can I test the same categorical variable across two populations?

I have data that looks a little something like this: ID Status 01 A 02 G 03 E ... ... 100 G You get the idea, I ...
125 views

### Chi Square Testing - binary outcome analysis

I have formed a contingency table for my binary outcome experiment that has been discussed in my previous question : binary outcome testing One of my hypothesis says that females are better at ...
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### Chi square for logical vectors: 2 row contingency table or 1 row vector?

I want to determine the independence between groups of logical variables. For example, for three groups, I want to know if the number of females (versus males) differs between the groups. I'm ...
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### Comparing contingency table distribution

I want to compare the distributions of $K$ contingency tables, where each table is $N \times M$. To make things clearer, let's work on $K=M=N=2$. Suppose I have a classical cases and controls test, ...
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### Test to use to measure the association of half-deciles

I'm querying a large (100 million row + ) SQL Server database and doing some preliminary work on the correlation between visits to the emergency room and total healthcare costs. I ran a query and the ...
302 views

### Comparison of entropy and distribution of bytes in compressed/encrypted data

I have some question which occupies myself for a while. The entropy test is often used to identify encrypted data. The entropy reaches its maximum when the bytes of the analyzed data are distributed ...
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### significance test to use for multiple conversions in an A/B test

What is the proper way to measure significance in an A/B test, when a visitor can potentially "convert" more than once? I understand a chi-square test or z-test are most often used for A/B testing, ...
135 views

### Null hypothesis and $\chi^2$ test

Which null hypothesis can be tested by a $\chi^2$ test? could you please write the description of the relevant null hypothesis or at least give an example. Thank you.
327 views

### Test for multinomial distribution

I have a sample of animals and a categorical variable of $L$ behaviors $i=1,...L$. I computed the proportions of this sample corresponding to each behavior category $p_{i}$, $\sum p_{i}=1$. Can I ...
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### Independence test for values between 0 and 1

I want to compare a set of frequencies and determine the p-value of their dependence. One of them is the null distribution of frequencies and the other is the distribution that I want to test. The ...
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### Appropriateness of K-S test and Kruskal-Wallis for assessing medical data set

I am analyzing some stats for a paper I am writing. I have statistics help available through my faculty but am not there for a couple of months so hoping you can help out. n = 463, 2 patient groups( ...
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### How to set the non-centrality parameter of the chi-squared distribution in terms of sample size for a power calculation

I am doing some problems on hypothesis tests on the variance, using a $\chi^2$ distribution. I need to find the power of the test, and I tried to write my own code in R. I don't know how to express ...
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### Relation between reduced chi square and Akaike criterion

In choosing the best fit between different curves, supposing the errors are distributed normally, I can do the following things: Calculate the reduced $\chi_r^2=\frac{\chi^2}{N_b-N_p}$, where $N_b$ ...
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### Does there exist some sample size threshold for choosing between the chi-squared test and the exact binomial test?

I'd like to use the exact binomial test to analyze some data, but the exact binomial test takes too much computation and is unnecessary when the sample size is larger because it can be approximated ...
1k views

### Chi square test on non-normal distributions

I'm a beginner in statistics and would like to understand one of the requirements for the chi-square test to work. It is that the random variable being measured has to follow a normal distribution. ...
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### Significance test of whether participants have more friends of the same sex

I've run into a simple problem - but no idea how to access it correctly. I've 85 people asked concerning their social network; first example: how many friends do you have. Second, what gender is each ...
4k views

### Can chi square be used to compare proportions?

I've read that the chi square test is useful to see if a sample is significantly different from a set of expected values. For example, here is a table of results of a survey regarding people's ...
1k views

### Statistical significance (chi squared) for percentages over 100%?

So, working in web analytics, it's common to use a chi-square test for A/B tests to test statistical significance. I often use a calculator like this: http://www.usereffect.com/split-test-calculator , ...