Chi-squared test in SciPy - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the Chi-squared test?

The Chi-squared test checks if there is a significant difference between expected and observed data in categories. It helps us see if two things are related or independent.

beginner

What are the two main types of Chi-squared tests?

1. Chi-squared test for independence: checks if two categorical variables are related.<br>2. Chi-squared goodness-of-fit test: checks if observed data fits an expected distribution.

intermediate

In Python's scipy library, which function is used to perform a Chi-squared test for independence?

The function is scipy.stats.chi2_contingency(). It takes a contingency table (observed counts) and returns the test statistic, p-value, degrees of freedom, and expected frequencies.

beginner

What does a low p-value (e.g., less than 0.05) mean in a Chi-squared test?

A low p-value means the observed data is unlikely if the variables were independent. So, we reject the idea that they are independent and say there is a relationship.

beginner

What is a contingency table in the context of the Chi-squared test?

A contingency table is a grid that shows counts of observations for combinations of two categorical variables. It helps organize data to perform the Chi-squared test.

Which scipy function is used for the Chi-squared test of independence?

A scipy.stats.ttest_ind

B scipy.stats.chi2_contingency

C scipy.stats.f_oneway

D scipy.stats.pearsonr

The correct function for Chi-squared test of independence is scipy.stats.chi2_contingency.

What does the Chi-squared test compare?

A Observed and expected frequencies

B Means of two groups

C Correlation between two variables

D Variance of a dataset

The Chi-squared test compares observed counts with expected counts under a hypothesis.

If the p-value from a Chi-squared test is 0.03, what should you do at a 0.05 significance level?

A Reject the null hypothesis

B Fail to reject the null hypothesis

C Increase the sample size

D Ignore the result

A p-value less than 0.05 means reject the null hypothesis of independence.

Which data structure is needed to perform a Chi-squared test of independence?

A List of means

B Time series

C Scatter plot

D Contingency table

A contingency table with counts of categories is required for the test.

The Chi-squared test is best suited for which type of data?

A Time series data

B Continuous data

C Categorical data

D Text data

Chi-squared test analyzes categorical data frequencies.

Explain how to perform a Chi-squared test of independence using scipy with a simple example.

Think about a table showing counts of two categories and how to check if they relate.

Describe what a p-value tells you in the context of a Chi-squared test.

Focus on what the p-value means about the relationship between variables.