Estimating quartiles from cumulative frequency
Estimating quartiles from cumulative frequency.
- Cumulative frequency is a running total. Plot it at the upper class boundary.
- Read the median at N/2, Q₁ at N/4 and Q₃ at 3N/4.
- The interquartile range is Q₃ − Q₁. Graph readings are estimates.
Example 1
Estimate the lower and upper quartiles to 1 d.
Lower-quartile position
Upper-quartile position
Example 2
Estimate the lower and upper quartiles to 1 d.
Lower-quartile position
Upper-quartile position
Your turn
Question 1Straight-line interpolation between class-boundary points.
Estimate the lower and upper quartiles to 1 d.
Check answer
Lower-quartile position
Upper-quartile position
Question 2Straight-line interpolation between class-boundary points.
Estimate the lower and upper quartiles to 1 d.
Check answer
Lower-quartile position
Upper-quartile position
Question 3Straight-line interpolation between class-boundary points.
Estimate the lower and upper quartiles to 1 d.
Check answer
Lower-quartile position
Upper-quartile position
Question 4Straight-line interpolation between class-boundary points.
Estimate the lower and upper quartiles to 1 d.
Check answer
Lower-quartile position
Upper-quartile position
Question 5Straight-line interpolation between class-boundary points.
Estimate the lower and upper quartiles to 1 d.
Check answer
Lower-quartile position
Upper-quartile position
Estimate the lower and upper quartiles to 1 d.
Lower-quartile position
Upper-quartile position
Estimate the lower and upper quartiles to 1 d.
Lower-quartile position
Upper-quartile position
Estimate the lower and upper quartiles to 1 d.
Lower-quartile position
Upper-quartile position
Estimate the lower and upper quartiles to 1 d.
Lower-quartile position
Upper-quartile position
Estimate the lower and upper quartiles to 1 d.
Lower-quartile position
Upper-quartile position