# McNemar Test Calculator

Test paired binary categorical changes with exact binomial or continuity-corrected chi-square McNemar test

> Canonical page: https://elysiatools.com/en/tools/mcnemar-test-calculator

- **Category:** Math & Numbers

- **Keywords:** mcnemar test, paired categorical data, before after test, exact binomial, p value, calculator

## Overview

The McNemar Test Calculator evaluates changes in paired binary data, such as before-and-after studies or matched-pair designs. By analyzing discordant pairs, it determines if a significant shift in proportions has occurred using either the Exact Binomial method or the continuity-corrected Chi-Square test.

## Inputs

- **Before Yes After Yes** (number)
- **Before Yes After No** (number)
- **Before No After Yes** (number)
- **Before No After No** (number)
- **Method** (select)
- **Alpha** (number)
- **Decimal Places** (number)

## When to use

- Analyzing the effectiveness of a treatment in a pre-test/post-test study with binary outcomes.
- Comparing the performance of two different diagnostic tests applied to the same group of subjects.
- Evaluating opinion shifts in a survey where the same individuals are polled at two different time points.

## How it works

- Enter the frequencies for the four possible outcomes: Yes/Yes, Yes/No, No/Yes, and No/No.
- Select the calculation method, choosing between Exact Binomial for small samples or Chi-Square for larger datasets.
- Set your significance level (Alpha) and preferred decimal precision for the results.
- Review the calculated p-value and discordant pair count to determine if the null hypothesis should be rejected.

## Use cases

- Medical researchers comparing patient symptoms before and after a specific clinical intervention.
- Marketing analysts measuring brand awareness among the same focus group before and after an advertising campaign.
- Quality control engineers testing if a machine recalibration significantly changed the pass/fail rate of components.

## Frequently asked questions

### What are discordant pairs in a McNemar test?

Discordant pairs are the cases where the outcome changed between the two observations, specifically the 'Yes to No' and 'No to Yes' counts.

### When should I use the Exact Binomial method?

Use the Exact Binomial method when the total number of discordant pairs is small, typically less than 25, to ensure statistical accuracy.

### Does this tool handle independent samples?

No, the McNemar test is specifically designed for paired or matched data where the same subjects are measured twice.

### What does 'Reject Null' mean in the results?

It indicates that the calculated p-value is less than your specified Alpha, suggesting the observed change is statistically significant.

### Why are concordant pairs ignored in the calculation?

McNemar's test focuses exclusively on the direction of change; concordant pairs (Yes/Yes and No/No) do not provide information about the shift between states.

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