Expected frequency
Expected frequency tells you how many outcomes you would expect in a category if the data follow the given proportions or probabilities.
Method
- Identify the total number of trials or observations.
This might be the total sample size, total spins, total people, or total items.
- Find the probability or proportion for the category.
Use the value given in the question. If there are several categories, make sure you use the correct one.
- Multiply:
[
\text{expected frequency} = \text{total} \times \text{probability}
]
If a proportion is given as a fraction or decimal, use it directly.
- Simplify the result.
If the answer is a fraction or exact value, reduce it fully. If a decimal is needed, write it clearly.
Check your answer
- The expected frequencies for all categories should add up to the total number of observations.
- If your answer is much larger than the total, recheck the probability or the multiplication.
Useful reminder
Expected frequency is not the same as actual frequency. It is the number you would expect on average, based on the given information.