Data cards
Warm-up
Investigate the evidence
Evidence board
Centre and spread: two sets can have a similar middle but very different variation.
Live data plot
Explore the data, then check your answer.
The maths
Mean = sum of observations ÷ number of observations.
Median = middle of the ordered observations.
Mode = most frequent value; some sets have no mode.
Range = maximum − minimum.
Quartiles: medians of the lower and upper halves, excluding the middle observation when the size is odd.
Interquartile range = Q3 − Q1.
Grouped mean estimate = sum(frequency × class midpoint) ÷ total frequency.
Frequency density = frequency ÷ class width. Histogram area represents frequency.
Box plot: whiskers end at the most extreme non-outliers, using 1.5 × IQR fences.