Types of data, quartiles and percentiles from raw and grouped data, the range, interquartile range and semi-interquartile range, and drawing and interpreting stem-and-leaf and box-and-whisker diagrams.
5 narrated scenes. Press play, listen and read along — the points appear as they are explained. Use ‹ Prev / Next › or the scene bar to jump to any scene.
Fifteen numbers tell you nothing until you organise them. A stem-and-leaf diagram and a box plot show the middle, the spread and the shape in seconds.
Narration uses your device’s built-in voice. No sound? Switch to “Captions only” — the captions advance on their own.
Copy these into your notebook in your own words — that is how they stick.
Qualitative (categories) vs quantitative (discrete counted; continuous measured).
Q₁ at (n + 1)/4; Q₂ at (n + 1)/2; Q₃ at 3(n + 1)/4.
Range; IQR = Q₃ − Q₁; SIQR = IQR/2.
P-th percentile at position P(n + 1)/100.
Interpolate: L + [(position − cf before)/f] × class width, using boundaries.
Ordered leaves and a key; shows every value.
Min, Q₁, median, Q₃, max; shows spread and skew; hides individual values.
Use median and IQR to compare two box plots.
3 quick games on this lesson. Earn XP and badges as you play — your best score for each game is saved. Games are for practice and do not change your exam readiness. More games in the Additional Mathematics Arcade.
8 items modelled on real CSEC Paper 1 questions. Choose one answer for each, then check. Aim for 80% or better. Work each item on paper first.
Write full answers, then reveal the mark scheme and tick the points you earned (27 marks in total). Show all your working — method marks count. Your answers are saved on this device.
Question 1 [13 marks]
The scores of 15 students in a test are: 62, 65, 67, 71, 74, 76, 79, 83, 84, 90, 92, 94, 99, 103, 108.
(a) Construct a stem-and-leaf diagram for the data, with a key. [3]
(b) Find the median, the lower quartile, the upper quartile and the interquartile range. [5]
(c) Draw a box-and-whisker plot of the data. (Check: scale, whiskers 62 and 108, box from 71 to 94, median line at 83.) [3]
(d) Calculate the 90th percentile. [2]
Question 2 [14 marks]
The heights of 40 students are: 140–149 (6), 150–159 (10), 160–169 (14), 170–179 (7), 180–189 (3).
(a) Construct a cumulative frequency table using the upper class boundaries. [2]
(b) Estimate the median height. [3]
(c) Estimate the lower and upper quartiles and the interquartile range. [4]
(d) Estimate the 90th percentile. [3]
(e) State one advantage and one disadvantage of a box-and-whisker plot for this data. [2]
Find these in your own past-paper booklets for extra timed practice. Items above are written in the style of these papers; any adapted from a specific question say so.