Choose a statistic that fits the data. State its unit and total, and check whether unusual values change the picture.
A frequency is a count. If 12 of 20 respondents walk to a park, the fraction is 12 divided by 20. Multiply by 100 to get 60%. The denominator, 20, is the total you are comparing against. This result describes respondents, not automatically all residents.
Check for missing responses and questions that allow several answers. Their category percentages may not add to 100% of respondents.
The invented first-journey times are 5, 5, 10, 15 and 40 minutes. To find the mean, add the values and divide by their number: (5 + 5 + 10 + 15 + 40) / 5 = 15 minutes.
The median is the middle value after putting the values in order: 10 minutes here. With an even number of values, take the mean of the two middle ones. The mode is the most frequent value: 5 minutes appears twice.
The 40-minute journey pulls the mean above the median. The median may better describe a typical central journey here, while the mean uses every value. Do not delete an unusual value just because it differs; check whether it is a recording error or a genuinely long journey. You can also find the mode of categories such as transport types, but cannot calculate a mean of category names.
Step by step
Check the data
Confirm unit, valid values, missing entries and the relevant denominator.
Calculate transparently
Show the total and count for a mean; order values for a median; count repeats for a mode.
Interpret
Explain what the summary shows and whether an unusual value affects it.
Worked example: Percentage points and relative change
If the walking share rises from 40% to 60%, that is an increase of 20 percentage points. Relative to the starting share, it is a 50% increase: (60 - 40) / 40 x 100. State which comparison you mean, and ensure the two surveys are comparable.
Watch out for this
Averages prove every person had the same experience.
An average summarises variation. Report the distribution or important exceptions when they matter to the question.
Check your understanding
For travel times 5, 5, 10, 15 and 40 minutes, which statement is correct?
- The median is 15 because it is the mean.
- The mode is 40 because it is the largest value.
- The mean is 15 and the median 10, with the long journey raising the mean.