A1.L.1Center & spread01/06
Center and spread — mean, median, IQR, standard deviation.
The dataset (9 test scores, sorted)
12,15,18,20,22,25,30,31,35
Step01of 06
Two questions describe almost any dataset: where is the center? and how spread out is it? Each has two common measurements.
| Mean (average) | →sum ÷ count — sensitive to outliers |
| Median (middle value) | →middle of sorted data — resistant to outliers |
| IQR (interquartile range) | →Q3 − Q1, the spread of the middle 50% |
| Standard deviation | →typical distance from the mean |