Shape of Data, Outliers and Best Measure of Centre

Before calculating anything, look at the shape of the data. In NSW Year 8 maths (NESA outcome MA4‑DAT‑C‑02) a set is described as symmetrical, positively skewed (tail to the right) or negatively skewed (tail to the left), together with its peaks, clusters, gaps and outliers.

You will measure how far an outlier pulls the mean while the median barely moves, then choose the best summary: the mean for marks that sit close together, the median for skewed data such as house prices, and the mode for the most common size. Examples include a 95 cm mulloway among small fish, a $2.4 million waterfront home and a batter’s innings of 142. It is part of Year 8 Investigating Data.