A test (typically of distribution, independence, or goodness of fit) or a family of distributions related to such a test.

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Three proportions testing null hypothesis

I have the following question. In a random sample of 250 people with low incomes, 155 are in favour of a new piece of legislation, while in random samples of 200 people with average incomes and 150 ...
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19 views

Chi square test with replicates

Is there anyway to do chi square (or any other ratio rest ) with replicates. For example, my data have measures of different time points, each time points has 4 replicates. The measures are discrete ...
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10 views

A/B testing zero inflated data

I am trying to conduct an A/B(/C) test to compare the performance of 3 different website pages but I'm facing issues regarding zero inflated data. I have data for each page regarding ...
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11 views

which test for means of coded, categorical discussion forum posts?

I'm trying to wrap my head around this problem, how to state it formally for analysis (what kind of study is it) and which test(s) to run: I am comparing the content of 2 discussion forums (the study ...
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13 views

Friedman's test help in R

I'm trying to figure out Friedman's test in R and am confused by some of the output. For example, consider two groups where the ranks are reversed. Thus Group 1 goes from 1:40, then group 2 goes from ...
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14 views

What to use when chi-square independence assumption is violated

I'm trying to describe the characteristics of the sexual partners of each participant. There are multiple partners per participant. All of the variables in my analysis are categorical, so originally I ...
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34 views

Which statistical test for women height?

Suppose women may have Blue or Red eyes. We make a first cheap research on a 100 women checking just one eye of each woman. So after the research we have results: At least one eye Blue have avg ...
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1answer
26 views

Ways to test bar charts with few bars to see if they come from the same distribution?

I have survey data with ordinal/categorical data. Most of the time the answers to question are Yes/No. I want to compare the bar charts (normalized) of yes/no from participants who gave a particular ...
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8 views

Generalized minimum chi-square estimators?

I need to implement the generalized minimum chi-square estimators (alternative to L-moments method and maximum likelihood estimate (MLE)) for estimate the parameters of the gamma distribution. My ...
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34 views

Non-zero mean and finite-variance Gaussian Squared R.V has Non-central Chi squared distribution, but how?

If $$X \sim \mathcal{N}(\mu,\sigma)$$ then $$X^2 \sim \frac{e^{-\frac{\left(\mu +\sqrt{x}\right)^2}{2 \sigma ^2}} \left(e^{\frac{2 \mu \sqrt{x}}{\sigma ^2}}+1\right)}{2 \sqrt{2 \pi } \sigma ...
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22 views

Difference in Chi-square calculated by anova from cph and coxph

Is there a difference between Chi-square (from coxph -> anova) and Wald Chi-square (from cph ...
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1answer
30 views

Testing if a interval scaled variable A and a nominally scaled variable B are independet when A is not normally distributed

We have a variable A which denotes a percentage between 0 and 1. The variable is not normally distributed but has a very left skewed distribution. About 5% of the observations are zero, most ...
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48 views

Relationship between gamma and chi-squared distribution

If $$Y=\sum_{i=1}^{N}X_i^2$$ where $X_i \sim \mathcal{N}(0,\sigma^2)$. i-e all $X_i$ are i.i.d normal random variables of zero mean with same variances. then $$Y \sim Gamma(\frac{N}{2},2\sigma^2).$$ ...
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1answer
19 views

Wald test in logistic regression and its relationship to Z-statistic

If I have Z-statistic values in regression analysis, how can I convert them to Wald statistcs? Can Wald value be negative?
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37 views

Parameter distribution from profile likelihood

This question is regarding profile likelihood to obtain CI of parameters. There is a published parameter values that best fits (using minimum chi square)the data for some mathematical model say ...
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6 views

Is there a BIC or AIC formula for correcting a G-statistic?

I am using the G-test (http://en.wikipedia.org/wiki/G-test) for scoring models with different numbers of parameters in a model comparison problem. Is there a BIC or AIC formula to correct a ...
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1answer
59 views

If $\frac{(2n-1)s^2}{\sigma^2} \overset{}{\sim} \chi^2_{2n-1}$, can I take the variance of both sides to get an equality relation?

I currently have a standard result regarding variances and it looks like: $\frac{(2n-1)s^2}{\sigma^2} \overset{}{\sim} \chi^2_{2n-1}$ that is, it is approximately a chi-squared distribution with ...
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40 views

Hypothesis testing based on Likert type data

I know this site is full of similar questions, but either their answers do not apply, or I'm missing something. I have data from a questionnaire. Responses are in the form of Likert items, some of ...
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41 views

Testing uniformity of data

I need to test if a vector of observed values are uniform distribution. Lets assume: This values are not a sample, but my entire universe. I have a dataset of 12000 observations, where most of the ...
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1answer
11 views

Confidence interval from summaries in JMP

If i only have mean, std dev. and number of observations is it then possible to generate af 95% confidence interval or a Chi squared test in JMP using only these summaries as input?
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24 views

A/B testing on non-stationary populations

I am running A/B tests on a website. The daily engagement level of the users varies wildly, with a strong weekly seasonality. (Basically, users who are willing to use the software on Sundays are more ...
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17 views

One model or 178 models?

I am doing a school project, where I am modeling next quarter's stock price using the information about the stock in the current quarter. The main goal is to see if we can find any statistically ...
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13 views

Error type I for $X_i \sim Exp(\theta)$

Let $ X_i$ be i.i.d $Exp(\theta)$ for i=1,...,4.We want to test $H_0: \theta =6$ versus $ H_1: \theta = 2$. Consider the following test: $$\text{Test: Rejects H_o} \iff \frac{X_1 + X_2}{2}>4.5$$ ...
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102 views

How to assess the incremental additive information of a new predictor in a Cox model using R?

I want to check whether the addition of the new predictor x3 improves the predictive information of a Cox model significantly or not. So far I have: ...
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1answer
90 views

3x3 contingency table: what to use instead of chi-squared test?

I have questionnaire data from subjects divided into 3 groups, G1, G2 and G3. Subjects had to answer a question, and they had the options A1, A2 or A3 to choose from. The correct answer depended on ...
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194 views

Using brute force to get exact p-value instead of Chi-Squared Test of Independence

Background I have the following contingency table ...
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1answer
16 views

Is it OK to remove columns with low numbers in before running a chi-squared test?

I'm looking at significant differences for conversion by browser using a chi-squared test. My table looks like this: ...
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279 views

Why are these two random variables identically distributed?

Let $(X_1, X_2, \ldots, X_i, \ldots, X_k)$ be $k$ independent, normally distributed random variables with means $\mu_i$ and variances $1$. Then the random variable $$ \sum_{i=1}^k X_i^2$$ is ...
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1answer
32 views

Survey data: finding the most significant predictors?

I have about 5,000 responses to a survey in which users were asked how strongly they agreed with a statement on a 5-point Likert scale. This response is my dependent variable - I want to find out what ...
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1answer
19 views

Dependent chi-squares vector: how to calculate cdf of $X_{(n)}$?

Consider a vector of central&1-degree Chi square distributed variable $(X_1, X_2,...,X_n)$, it is simple to calculate the cdf of $X_{(n)}$ (maximum of order statistics), when they are independent. ...
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1answer
72 views

chi-squared test when variables dependent

For a square matrix, is it appropriate to use a chi-squared distribution when each level of the variables are assumed to have the same overall frequency? Specifically, I'm analyzing a dataset of the ...
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45 views

chisq.test with R

I want to do a Goodness-of-Fit test of my data and the Weibull-distribution. I have estimated the Weibull distribution using the survreg-function in R. Now I want ...
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25 views

Chi-squared test and logistic regression

Is there a relation between chi-squared test and logistic regression model in a similar manner between ANOVA and linear regression?
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31 views

Chi-Squared Goodness of Fit Test Alternative? - Zero Can't Be in Denominator

I have 5 zones(categories) in which a certain percentage of total sinkholes exist. I have 5 different maps that I am testing to see which one provides me with the best fit to my expected percentages ...
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38 views

Is the chi squared test appropriate?

I have claim data from two different insurance administrators. From each administrator, I have calculated the relativity of miles driven per year based on claim data. I want to determine whether ...
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1answer
13 views

What's the right test to use to find significance in a table of incidence rates?

I have some data about conversion rates on different browsers, as follows. ...
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22 views

$\chi^2$ test vs F-test in feature selection

In the context of feature selection for classification, does it make sense to use one filter based on $\chi^2$ test and the other one based on F-test? Or they are "interchangeable"?
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1answer
52 views

stats for 2x4 contingency table with both very large and small or zero counts

I have 7000 2x4 contingency tables with count data. They represent a particular position in a genome and the number of times each dna nucleotide is observed at that position in 2 different ...
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12 views

Chi-Square analysis after ANOVA and correlations failed to give results

I have a continuous dependent variable and two independent grouping variables of age and gender. Age has three groups and gender two (obviously!). Now ANOVA has shown no differences across both. ...
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1answer
31 views

Please help me interpret this goodness of fit test

In the game of Bridge, 52 cards are distrubuted randomly among 4 players, each player ending up with 13 cards. I implemented a random number generator using the RNGCryptoServiceProvider form the ...
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2answers
18 views

Calculating chi-squared values for percentages?

I'm using scipy and I'd like to calculate the chi-squared value of a contingency table of percentages. This is my table, it's of relapse rates. I'd like to know if there are values that are ...
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23 views

Visualise significant differences in a contingency table?

I'm working with pandas and scipy, and I would like to find a quick way to visualise unusual values in a contingency table. Say this is my contingency table: ...
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2answers
41 views

Logistic regression, Chi-square, and study design

I have a study in which I have developed a new predictor (binary) for a disease (also a binary variable). The study has two parts. In the first part, I want to test if my predictor is strongly ...
2
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1answer
35 views

Can we run a chi squared test on a normalized function?

Hi I am fit a maxwell distribution and attempt to find the chi squared value in two cases: When the data is normalized. When the data is un-normalized. My problem is that the two ...
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8 views

post-hoc multiple comparisons with chi squared using spss v. 22

I am carrying out an analysis using a 4$\times$2 crosstab. I found an overall significant difference but I would like to find if there are significant differences among the 4 groups. Is there a way ...
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2answers
21 views

Chi-square test for Homogeneity problem (cell count less than 2)

My table of chi-square test for homogeneity has 3x5 cells, 3 samples to a likert scale item. Most cells in the table have a frequency count of less than two, so it is recommended to discard the column ...
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2answers
134 views

Confidence Interval on a random quantity?

Suppose $\vec{a}$ is an unknown $p$-vector, and one observes $\vec{b} \sim \mathcal{N}\left(\vec{a}, \frac{1}{n} I\right)$. (For example, the sample mean based on $n$ observations of i.i.d. normal ...
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33 views

Chi-squared calculation for (nonlinear) model goodness of fit for data with trials

I would like to be certain of how to calculate the $\chi^2$ value for this scenario: We desire a measure of the goodness of fit of a nonlinear model to a data set. The data consists of many ...
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70 views

Using chi goodness of fit to test if data comes from normal distribution

The problem gives 50 observations and then asks to check whether the data comes from a normal distribution. For instance if these are your observations then how would you go about testing to see if ...
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22 views

What statistical test to use for A/B testing

I'm trying to understand how A/B testing works for a simple 2x2 contingency table. I have found two different types of solutions: 1) Calculate an aggregate probability of conversion assuming that ...