Order the data. The median splits the ordered list; the lower and upper quartiles Q_1,Q_3 are the medians of the lower and upper halves. In this method exclude the overall median from both halves when the count is odd. Range =maximum-minimum; interquartile range IQR=Q_3-Q_1. The range uses the extremes, while the IQR describes the spread of the middle half and is less affected by a single extreme. Example For 2,4,4,6,8,10,10,12, the median is 7, Q_1=4, Q_3=10. Thus range =12-2=10 and IQR =10-4=6. Quartiles divide ordered positions into four parts. Ties can mean more than 25% of observations are at or below Q_1; do not assume each visible interval contains exactly a quarter of the observations in every small data set.

Order the data. The median splits the ordered list; the lower and upper quartiles \(Q_1,Q_3\) are the medians of the lower and upper halves. In this method exclude the overall median from both halves when the count is odd.

Range \(=\text{maximum}-\text{minimum}\); interquartile range \(\mathrm{IQR}=Q_3-Q_1\). The range uses the extremes, while the IQR describes the spread of the middle half and is less affected by a single extreme.

For \(2,4,4,6,8,10,10,12\), the median is 7, \(Q_1=4\), \(Q_3=10\). Thus range \(=12-2=10\) and IQR \(=10-4=6\).

Quartiles divide ordered positions into four parts. Ties can mean more than \(25\%\) of observations are at or below \(Q_1\); do not assume each visible interval contains exactly a quarter of the observations in every small data set.

Statistics

Cambridge IGCSE Mathematics 0580. Initial catalogue covers the assessed demands of February/March 2026 Paper 22; further Core and Extended mappings require paper-level scope review.

Quartiles, range and interquartile range

Quartiles, range and interquartile range