Unit 3 · 1.3

Pie graphs, dot plots, stem-and-leaf

Percent of n, dot counts, stems and leaves

Practice 0/8Checkpoint best 0%

Rule cards

Percent = f ÷ n × 100; degrees = f ÷ n × 360°. 'A or B' → add the two percents; 'how many of 500' → percent × 500.

Traps

Added the wrong slices.
'cats or rabbits' → added cats and dogs
✓ read the labels first, then add only the named slices
Reported the percent as the number of people.
20% of 500 → 20 people
✓ 20% × 500 = 0.20 × 500 = 100 people
Used a different total than the one asked.
% × the number of slices
✓ 'of 500 people' → the base is 500

One dot per data value: n = count every dot; 'how many have 2' = dots above 2; mode = tallest stack.

Traps

Miscounted a stack.
counted the axis tick as a dot
✓ count dots only, column by column
Took the biggest x-value as the mode.
mode = rightmost dot
✓ mode = the TALLEST stack
Gave the stack height when the value was asked (or the reverse).
mode → 6 dots instead of the value 2
✓ read what the question asks: the value (x) or how many (dots)

Stem = all digits except the last; leaf = the last digit. Highest = last stem + its last leaf; lowest = first stem + first leaf.

Traps

Counted a repeated leaf once.
2 | 0 1 1 1 4 → 3 values
✓ repeated values get repeated leaves: 2 | 0 1 1 1 4 5 7 8 9 = 9 values
Combined a leaf with the wrong stem.
7 | 1 read as 17
✓ 7 | 1 = 71
Left leaves out of order.
write leaves as they come
✓ leaves are written in increasing order