Bring together comparisons, box plots, two-way tables and sampling.
Example 1
Group A has 6 scores with mean 10. Group B has 8 scores with mean 24. What is the combined mean? Give an exact fraction or decimal.
Show worked answer
Answer: 18
- Group totals are 6×10=60 and 8×24=192.
- Divide their combined total 252 by the combined count 14:18.
- The groups have different sizes
- simply averaging the two means is not valid.
Example 2
What fraction of all people walk?
Show worked answer
Answer: 136
- The Walk column total is 12
- 136.
Example 3
A bar chart starts its vertical axis at 90 rather than 0, making scores of 95 and 100 look very different. What should you check?
Show worked answer
Answer: The axis baseline and scale
- A truncated baseline can exaggerate differences in bar lengths.
- Read the scale before comparing.