What this lesson teaches
I can organise fieldwork data and analyse its patterns with counts, averages and comparisons.
Syllabus K335, Topic 1.3, Key Question 3. How to process and analyse data?
I can present fieldwork findings with clear maps, graphs, sketches and text.
Syllabus K335, Topic 1.3, Key Question 4. How to present findings?
I can read maps, graphs, photographs and texts, and separate what they show from what they suggest.
Syllabus K335, Topic 1.3, Key Question 4 (part). How to present findings?
Make a guess
Survey A: 75% of 40 people cycle to school. Survey B: 40% of 100 people cycle. Which survey found more cyclists?
- Survey B, with 40 cyclists against 30.
- You cannot tell from percentages alone.
- They found the same number of cyclists.
- Survey A, because 75% is much bigger than 40%.
Show the answer
Survey B, with 40 cyclists against 30.
A percentage needs its total. 75% of 40 is 30 people, while 40% of 100 is 40 people, so the smaller share holds more cyclists.
A bigger percentage does not always mean more people, so always check the total behind each percentage.
A pie chart splits one total into shares. In the practice survey, each of 20 people chose one main way to travel: 12 walk, 6 take the bus and 2 go by car. Walking is 12 / 20 x 100 = 60%. Bus is 30% and car is 10%.
To draw a sector, multiply its fraction by 360 degrees. Walking is 216 degrees, bus 108 and car 36. Together they make 360.
This only works if each person is in exactly one category. If people can choose several, the shares no longer add up. Account for missing answers too.
Check the total before comparing pies. In a second sample, 50% of 100 people walk. That is 50 walkers, more than the 12 in the first sample, even though 50% is smaller than 60%. Only treat two charts as evidence of change if the question and sampling method were the same.
- Percentage
- Count / total x 100.
- Sector angle
- Count / total x 360 degrees.
- Check the total
- A bigger share can be fewer people.
Step by step
Check the whole
Know the total; one category per person.
Work out shares
Count / total x 100 for %, or x 360 for degrees.
Compare carefully
A smaller total can hide a bigger count.
Worked example: Bigger share, fewer people
The 20-person sample has the higher walking share: 60% against 50%. But the 100-person sample has more walkers: 50 against 12. Use the comparison that answers your question.
Watch out for this
A 60% slice always has more people than a 50% slice.
Only if the totals are the same. Multiply each share by its own total first.
Check your understanding
Which has more walkers: 60% of 20 people or 50% of 100 people?
- 60% of 20, because 60% is the larger share of its group.
- They are the same because both are percentages.
- 50% of 100, because that is 50 walkers, not 12.
Show the answer
50% of 100, because that is 50 walkers, not 12.
Yes. Always convert back to actual numbers.