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

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Goodness of fit tests in R

I have a population of 663 random balls drawn. The interval of this population's values is [1,27]. I want to do a Goodness of fit test to proof if it has a gamma ...
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15 views

Robust one sample tests of variance or scale

A common one sample test for variance is the chi-square test, e.g., http://www.itl.nist.gov/div898/handbook/eda/section3/eda358.htm. What are some robust testing alternatives for variance when the ...
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34 views

McNemar's test vs chi-squared test for before & after data with different people from the same population

I have 2 proportions I want to compare. They are from the same population but at different time periods, in between which there was an intervention. H0: Proportion in Period#1 = Proportion in Period#...
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33 views

Can I compare chi-square values for goodness of fit tests to see which observed distribution deviated most from its null distribution?

I have a series of goodness-of-fit tests using chi-square a few of which are below, $$ \begin{array}{r|r|c} \text{df} & \chi^2 & \text{Reject } H_0 \\ \hline 49 & 1744.68 & \text{Yes}...
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59 views

Why is the mean of a Chi Square distribution equal to the degree of freedom?

Is this part of the definition of a Chi Square distribution? Or is it deduced from another property? In which case, what is the proof?
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1answer
23 views

Performing a chi-squared test with overlapping observations

I have a process that can be modeled by looking at the occurrence of particular patterns in a 12 digit binary string to determine if those patterns occur more or less often than they would randomly. ...
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28 views

R squared and higher order polynomial regression

The plot below shows the saturation of a road against the impact on journey time (normalized to free flow journey time). The blue (BPR function) curve presents a standardized model used in the field ...
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96 views

Estimate of parameter of exponential distribution with binned data

I have the following data, which can be modeled by exponential distribution ...
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1answer
28 views

why are the degrees of freedom for a chi-square test on a 2x2 contigency table always 1?

I know the "formula" is (# rows - 1) * (# columns -1). However, shouldn't the design of the experiment or observational study being conducted make a difference? The only experimental design I can ...
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14 views

How can I get R to give me a pearson stat on a poisson regression? [closed]

In particular the book I'm using shows it with the regression output, is this an old version or can I get R to do this too?
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1answer
37 views

Determining an effect of a seatbelt enforcement and a public outreach program in a town

We conducted a seat belt use observation study in two similar sociodemographic towns with different media markets. We sampled two towns and measured outcomes in a pre and post format. One town was a ...
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24 views

mle for the binomial distributed data

For example i have folowing dataset of number of boys in families that have 5 kids: 0 boy - 34(number of such families) 1 boy - 128 families 2 boys - 233 families 3 boys - 267 families 4 boys - 144 ...
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54 views

Why Yates correction in McNemar's Test subtract 1?

McNemar's test statistic is given by: Yates's correction defines something like this: However, the correction for the McNemar's test statistic requires 1 (not ...
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10 views

Which test is appropriate when comparing proportions of a sample to a subgroup of that same sample?

I have sample of patients and their demographic information. A subset of this sample is identified as having a particular genetic marker. I'd like to know if the subset with this genetic marker have ...
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6 views

Chi-Square Difference test, set correlation to one [migrated]

I'm working on my master thesis and I'm not sure how to interpret an error message by R. I have 5 latent Variables (DI, PR, BQ, RA and RV). Since the Fornell Larcker Kriterium is in some cases not met,...
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102 views
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1answer
31 views

How to relate 2 sets of classifications (types of runners & motivations)

I am currently writing a proposal and am confused regarding which statistical method I should use. I aim to examine the motivation of runners in participating a charity marathon. It will use runners ...
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25 views

Comparing and ranking differentiating attributes across groups

I'm looking for some help on how to approach this problem. Say I have two or more groups of people. Each group has characteristics and attributes. For example, say we have the following two groups: ...
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14 views

Which observed frequency in a 2x2 contingency table is responsible for rejection of H0?

I'm carrying out a study on reported deaths of vultures (Gyps fulvus) in the Apennine mountains, Italy. I've performed a chi-square test on a 2x2 contingency table relating gender (male, female) to ...
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36 views

Chi-square and R: Calculate matrix of statistical significances between results

First of all, I would like to apologize if this is an duplicate of an earlier question. I find it hard to believe that I am the first person to ever have this sort of problem, but I am so far out of ...
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1answer
35 views

Anova on logistic regressions linearity

I'm trying to find out if my numeric predictors have a linear relation to the logit of my logistic regression. I tried to use the lrm fit in the rms package where I have used 3 knot cubic spline on ...
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18 views

How to propagate “model covariance” into a covariance matrix?

I have a theory $f$ (actually a set of coupled non-linear differential equations) that, from a vector of $n$ initial conditions $\vec x$, is able to predict $m$ values $f(\vec x) = \vec y$. I can ...
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10 views

Compare percentages

I am analysing pre-analyical errors in diagnostic labs. There are 15 types of different errors in the lab (such as hemolysed samples, clotted samples, insufficient volume, etc). Each of these errors ...
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4 views

Comparing set of counts with different n sample and many zeros.

I had a look of may treats and find different pieces here and there but I cant figure out how to do this "simple" comparison. I have 2 counts (obtained with different methods but assuming from same ...
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28 views

Why does the J-test yield a $\chi^2$ distribution?

My econometrics professor recently introduced us to the J-test. To perform the J-test, he gave us the following procedure: Estimate $\mathbf{b}^{2SLS}$ and using this, define $\hat{U}_n$ residuals ...
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26 views

multivariate chi-square distribution R/Simulation

Is there some R package that calculate the quantiles\percentage of some vector of multivariate chi-square distribution? If there isn't can I simulate these percentage somehow? Thanks a lot.
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41 views

Chi square test in a contigency table with sampling zeroes

im trying to estimate if an association exists between two variables in a 7x5 contingency table (the type of prosthesis with the type of complication). The table contains a lot of sampling zeroes and ...
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17 views

SCORE METHODS CONFRONT

I would like your opinion. my data is score (before and after therapy) on radiographs made with x-ray instrument and score based on the judgment of the doctor. I thought I create a new variable which ...
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2answers
64 views

Confidence & conclusion in rare event analysis

I am looking at the http://www.nejm.org/doi/full/10.1056/NEJMoa021134 paper and don't understand how they made their conclusions. According to the data in Table 1 they analyzed 440655 vaccinated ...
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1answer
14 views

Chi squared test sample size

I'm trying to figure out if there's a difference across the main capitals in Europe and the voting preference of their inhabitants for extreme right political parties. So far I have categorized all ...
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9 views

Significance test for yearly collected average data

I have data from a random survey that is collected every year. One of the variables are the expenditures per person for health care spent in the corresponding year. Another variable is the percentage ...
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2answers
54 views

How to proceed with chi square test in R if one line has zeros?

I am trying to program with R. My categorical data is in a table of 5*5. However, the 5th line has only zeros. When I run the chi square test in a software program, it returns the result INVALID. But ...
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1answer
28 views

Chi-square test of equality for 25th and 75th percentile

I would like to examine the equality of the 25th and 75th percentile between two groups. One way would be to apply Mood's test adapted to the 25th percentile (and then to the 75th): Construct the ...
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1answer
27 views

Fisher and chi-squared assumptions/limitations not met

Fisher exact test is said to be used with a total sample (n) < 1000, whereas chi-squared test should be used when each category (/cell in a contingency table) >=5. What if you have an mxn ...
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22 views

Independence test for three categorical variable

I want to know if my use of the $\chi^2$ test of independence is valid. I have three binary categorical variables, $X,Y,Z$, and I want to test the following hypothesis. If you are in the group $X = 1$...
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21 views

Why does the test statistic from Pearson's chi-squared test for independence have a chi-squared distribution?

Why does Pearson's chi-squared test for independence have a chi-squared distribution? I can see that the numerator is squared, but doesn't the division by $E_i$ affect the distribution? $$ \chi^2 = \...
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1answer
31 views

Difference between logistic regression and chi-square for analysis with no covariates?

I have a binary response variable (0s and 1s), the distribution of which that I want to compare to chance. I understand I could use logistic regression or a chi-square test to do this and that these ...
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1answer
18 views

Is a Fisher exact test for count data appropriate with an ordered factor?

I have the following contingency table: ...
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15 views

Finding discrepancies in distances between random variable samples

There are $N$ independent and unknown points $p_i$, $q_i \in \mathbb{R}^3$, $i \in [1, N]$. I want to find if the pairwise squared Euclidean distance of each $i$ pair is the same for all of them, or ...
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18 views

Correct equation for Breslow-Day statistic in homogeneity test of odds ratio

In Statistical Methods of Cancer Research; Volume 1 - The analysis of case-control studies the authors Breslow and Day derive a statistic to test for the homogeneity of combining strata into an odds ...
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1answer
72 views

Why is a low (<1) chi-square measure unlikely when degress of freedom are high?

If the chi-square measures variability, where 0 is no variability and a very small measure is no variability, shouldn't all chi-square distributions be shaped like the dof-1 distribution, where the ...
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48 views

p-value interpretation of Jonckheere Terpstra:one-sided or two-sided

I am using the Jonckheere-Terpstra test in order to validate the pooled t-test results. Basically, I like the JT test because of its non-parametric nature. Basically, I am now trying to understand ...
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17 views

Combining independent observables for the same quantity, how to check independence

Let's assume we have a set of observations $\{x_i\}$ of a physical quantity $x$. We have a model $x=X(y)$, where $y$ is a free parameter. Let's assume that we have two distinct observables, $f(x)$ and ...
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7 views

One Response Value Fails for Proportional Odds Assumptions

I am analyzing placement scores on the response of students' grades for various courses. I have used a Chi-Sq test with the likelihood ratio to check the proportional odds assumption. For one of the ...
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34 views

How to evaluate the combined effect of 2 variables?

I'm trying to analyse the effect of smoking on health. The health variable is binary(healthy or not) but there are 2 different exposures to smoking(active=variable A and passive=variable B). Variable ...
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1answer
14 views

Does the sample size for the dependent variable should be the same for all the values of the independent variable in Peason Chi-square?

I have a question about the sample size when using chi-square test of independence or multinomial logistic regression. I would if you provide me with your feedback since I search a lot and I could not ...
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6 views

Difference between expected spending and spending observed. What kind of statistical analysis should I apply?

I would like some advice from you about what kind of statistical analysis I could do about that data. My case is as follows: According to a research I have the information that the financial health ...
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34 views

Multiple Hypothesis Testing with Categorical Variables and Alternatives

Suppose we have a variable $Y_i$ which is a binary categorical variable, and we have a variables: $X_{i,1}$, $X_{i,2}$, ....$X_{i,n}$ ($i=1,2,....N$ where $N$ is sample size, and $n$ is the number of ...
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1answer
60 views

Mode of the $ \chi^2 $ distribution

I've been studying a statistics textbook that makes a claim that the $ \chi^2 $ distribution with $ k $ degrees of freedom has a mode at $ k - 2 $ without proof. (Wikipedia seems to agree) Why is this?...
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26 views

Calculating p-value based on Chi-Square vs Z-Test incl Standard Error

I have been testing the significance levels for my various a/b tests. Degree of freedom is 1 so there's not a lot of complications here. So far I've been calculating my results using Chi-Squared ...