Measures of centre/spread

Read a dot plot to find the mode (tallest stack), median (middle dot), and range (first-to-last occupied value), and calculate the mean, for a data set -- including working backwards from a given mean to find a missing value, and judging which measure of centre best represents a data set that contains an outlier. Discourage the word "average" in favour of naming the specific measure. Distinct from the existing 9MAT-derived lo-calculating-averages-and-range, which is entirely computation-only (a list of raw numbers, no diagram anywhere); this LO's task decks embed a live \PicStatisticsDotPlot diagram in every card, so students read three of the four measures directly off a genuine display before calculating the mean.

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Learning objective overview

Master Teaching Guide coverage for this objective.

Resources

Terminology

  • Mean (Average)
  • Median (Middle)
  • Mode (Most Common)
  • Range
  • Spread

Task goals

  • Read the mode (tallest stack) and range (first-to-last occupied value) directly off a dot plot.
  • Read the median off a dot plot, correctly handling both an odd count (single middle dot) and an even count (mean of the two middle dots).
  • Calculate the mean of a data set shown on a dot plot.
  • Work backwards from a target mean to find a missing data value.
  • Judge whether the mean or the median better represents a "typical" value when a data set contains an outlier, and justify the choice.
  • Explain why the range is far more sensitive to a single outlier than the median is, and recognise "average" as ambiguous shorthand for a specific measure of centre.

Key skills

  • Mean
  • Median
  • Mode
  • Range
  • Spread
  • Measures of centre

Quick stats

  • 0 total questions
  • 3 difficulty levels
  • Answers included
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