Linked Questions

60
votes
2answers
65k views

What is the relationship between a chi squared test and test of equal proportions?

Suppose that I have three populations with four, mutually exclusive characteristics. I take random samples from each population and construct a crosstab or frequency table for the characteristics ...
12
votes
2answers
3k views

The $z$-test vs the $\chi^2$-test for comparing the odds of catching a cold in 2 groups

I just read in a rather well-respected (popular) science magazine (the German PM, 02/2013, p.36) about an interesting experiment (without a source, unfortunately). It caught my attention because ...
9
votes
1answer
3k views

chi squared test or Z test? [duplicate]

I have an outcome from a biological experiment, where I have counted the number of dead cells upon a mutation. For example, in once case - out of 120 cells we saw 16% of the dead cells, but our ...
9
votes
2answers
5k views

Correlation among categories between categorical nominal variables

I have a data set with two categorical nominal variables (both with 5 categories). I would like to know if (and how) I am able to identify potential correlations between the categories from these two ...
4
votes
1answer
1k 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 ...
6
votes
0answers
7k views

Assessing A/B test results using Python [closed]

Problem's setting Assume having results of an A/B test. You let you users experience two variants of your website and you counted how many converted: ...
4
votes
1answer
867 views

Test of proportions or chi-squared? [duplicate]

These data are from an A/B test of free trials to conversion. Someone can sign up for a 30 day free trial of the product. If they like it they stay on and become paying customers. By default (A), when ...
3
votes
1answer
2k views

Comparing logistic regression models with AUC ROC in R vs Stata

I am fitting a logistic regression model for the likelihood of patients suffering morbidity after surgery. The most commonly used prediction tool at the moment is POSSUM (Physiological and Operative ...
2
votes
2answers
1k views

T Test or Chi Square?

There are 2 variables, City and No Of Matches won. Variables: 1City Sydney Canberra 2No Of Matches Won? Sydney: 200 out of 300 Canberra: 210 out of 300 Question: Is team Canberra ...
1
vote
0answers
1k views

SPSS Categorical Data: Residuals in Crosstabs

I would like to know what's the difference between the standardized residuals and the adjusted standardized residuals in cross-tabs cell display in SPSS? The following definitions are the ones that ...
0
votes
0answers
400 views

Confusion about z-test and chi square test on a very basic example

I am confused with the difference between z-test and chi square test. In book Agresti 2007 An introduction to categorical data analysis, page 9, the author had an example of testing Do a majority ...
1
vote
0answers
63 views

When I compare two samples with a chi squared, should I compare one sample against a combination of the two?

I have a categorical variable for measured for two samples and I want to see if this variable differs significantly between the samples. I want to do a chi-squared test, with the samples as the ...