Mean, median, mode and range
The four KS2 statistical measures. Year 6 expects all four; Year 5 introduces mean.
Mean: add all values, divide by count. Median: middle value when sorted. Mode: most frequent value. Range: largest minus smallest. Year 6 SATs may ask for any of the four; the question wording is precise about which one.
Worked examples
Set: 4, 7, 3, 9, 7. Sorted: 3, 4, 7, 7, 9.
Mean = (4+7+3+9+7)/5 = 30/5 = 6.
Median = 7 (middle of sorted). Mode = 7 (twice). Range = 9-3 = 6.
Frequently asked questions
Even count for the median?
Take the mean of the two middle values. {2, 4, 6, 8} median = (4+6)/2 = 5.
Multiple modes?
‘Bimodal’ = two modes. SATs questions usually have a single mode.
Range as a measure?
Range gives the spread but is sensitive to outliers. KS3/GCSE introduces interquartile range as more robust.