Higher only · box plots
Box plots.
Five numbers,
one picture.
and how to
compare two of them
a box plot shows —
Five values
lowest · lower quartile · median
upper quartile · highest
step 1 of 4
Find the five values
1. In order. The median is the middle: 8.
2. Quartiles: the middle of each half.
✓ Lowest 3, highest 15
put them in order first
step 2 of 4
Draw it
1. Mark all five values above the scale.
2. Box LQ to UQ, whiskers to the ends.
✓ The line inside the box is the median
step 3 of 4
Range and IQR
1. IQR = 12 − 5 = 7: the width of the box.
2. Range = 15 − 3 = 12: whisker to whisker.
✓ The box holds the middle half
step 4 of 4
Compare two
1. B has the higher median: 10 against 8.
2. B has the smaller IQR: more consistent.
✓ One average, one spread, in context
box plots —
Box
lower quartile to upper quartile
Line in the box
the median
Compare
medians, then IQRs, in context
Smaller IQR: more consistent.
Say what that means in context.
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