04 / 12 · Read a set of numbers
Does the average describe most people?
Calculate a mean and a median, and see why they can tell different stories.
Builds on Which group are you counting in?
Go to practice ↓A question to keep in mind
Five waiting times: 2, 3, 3, 4, 18 minutes. Would 'usually six minutes' be a good summary?
The mean adds every value and divides by the count. Here the total is 30 minutes across 5 visits, so the mean is 6 minutes. The unusually long wait pulls it upward.
The median sorts the values and takes the middle. Here that is 3. With an even count, take the mean of the middle two. Neither summary tells you every person's experience.
Work through an example
- Add: 2 + 3 + 3 + 4 + 18 = 30.
- Mean: 30 / 5 = 6 minutes.
- The sorted middle is the third value: 3 minutes.
Your turn
0 / 3For 2, 3, 3, 4, 18 minutes, fill in the mean and median.
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- Mean: 6 min
- Median: 3 min
The mean is 6, the median is 3. Four of the five waits are shorter than the mean.
If the last wait changes from 18 to 38 minutes, which summary changes?
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The mean changes, but the median stays at 3.
The new mean is 50/5 = 10 minutes. The sorted middle is still 3. This shows how an extreme value can pull the mean.
Four waiting times are 2, 4, 6, 20 minutes. What is their median?
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- Median: 5 min
The middle pair is 4 and 6, so the median is (4 + 6)/2 = 5 minutes.
Bring it back to your own work
Write five made-up waiting times. Make their mean larger than their median, then explain which value caused the difference.
Statistical literacy: directory, audit and transfer assessment
How do I retain independent judgment when using AI here?
Keep your own answer before consulting an AI candidate. Check sources, calculations, inference and conditions; explain adoption or rejection. Then solve a new-context task independently and apply the checks to this lesson.
Practice the verification workflow and keep a recordMy learning status
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