What is expected frequency?

What is expected frequency?

• A. The observed counts
• B. The predetermined expected counts for each category
• C. The sum of all observed counts
• D. The standard deviation of counts

Answer: (B)

In chi‑square analyses, the expected frequency is the number of observations you would expect in a category if the null hypothesis were true. It’s a prediction based on the null model, not what you actually observed. For a contingency table, the expected count for a category is computed from the margins (row and column totals) as (row total × column total) / grand total. For a goodness-of-fit test, it’s the total count times the hypothesized proportion for that category. This is why it’s described as predetermined or expected for each category—the counts you’d expect under the null. The observed counts are the actual data, the grand total is the sum of observed counts, and the standard deviation of counts measures variability, not the predicted counts under the null.

In chi‑square analyses, the expected frequency is the number of observations you would expect in a category if the null hypothesis were true. It’s a prediction based on the null model, not what you actually observed. For a contingency table, the expected count for a category is computed from the margins (row and column totals) as (row total × column total) / grand total. For a goodness-of-fit test, it’s the total count times the hypothesized proportion for that category. This is why it’s described as predetermined or expected for each category—the counts you’d expect under the null.

The observed counts are the actual data, the grand total is the sum of observed counts, and the standard deviation of counts measures variability, not the predicted counts under the null.