How Do You Calculate P-Value

In statistical hypothesis testing, the P-value is a crucial metric that helps researchers assess the strength of evidence against a null hypothesis. It quantifies the probability of observing a test statistic as extreme as, or more extreme than, the one obtained during the experiment, assuming the null hypothesis is true.

Formula: The P-value is calculated based on the observed and expected values, involving a statistical formula that considers the distribution of the test statistic under the null hypothesis.

How to Use:

  1. Input the observed value in the designated field.
  2. Input the expected value in the respective field.
  3. Click the “Calculate” button to obtain the P-value.

Example: Suppose you have observed 45 occurrences of an event, but you expected only 40 based on previous data. Enter 45 as the observed value and 40 as the expected value to find the P-value.


  1. What is a P-value?
    • The P-value is a measure that helps determine the strength of evidence against a null hypothesis in statistical hypothesis testing.
  2. Why is the P-value important?
    • A lower P-value suggests stronger evidence against the null hypothesis, indicating that the results are statistically significant.
  3. How is the P-value interpreted?
    • A P-value less than a chosen significance level (e.g., 0.05) indicates that the null hypothesis is unlikely, and the results are significant.
  4. Can the P-value be greater than 1?
    • No, P-values range from 0 to 1, where lower values indicate stronger evidence against the null hypothesis.
  5. What is the significance level in hypothesis testing?
    • The significance level, often denoted as alpha (α), is the probability of rejecting the null hypothesis when it is true. Commonly set at 0.05.

Conclusion: Understanding how to calculate the P-value is essential for making informed decisions in statistical analysis. This calculator provides a quick and accessible way to compute the P-value based on observed and expected values, facilitating rigorous hypothesis testing.

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