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Topic: Statistical Measures (Higher - Unit 1)

Specification References: S3.3h S3.3h Calculate median, mean, range, mode and modal class. Calculate quartiles and inter-quartile range.

Candidates should be able to:

• use lists, tables or diagrams to find values for the above measures
• find the mean for a discrete frequency distribution
• find the median for a discrete frequency distribution or stem-and-leaf diagram
• find the mode or modal class for frequency distributions
• calculate an estimate of the mean for a grouped frequency distribution, knowing why it is an estimate
• find the interval containing the median for a grouped frequency distribution
• calculate quartiles and inter-quartile range from a small data set using the positions of the lower quartile and upper quartile respectively and calculate inter-quartile range
• read off lower quartile, median and upper quartile from a cumulative frequency diagram or a box plot
• find an estimate of the median or other information from a histogram
• choose an appropriate measure according to the nature of the data to be the ‘average’

Notes

This reference includes all the requirements of S3.3 and some additional requirements for the Higher tier only.

In large data sets on a cumulative frequency diagram, the position of the lower quartile will be accepted as  or , the position of the median will be accepted as  or  and the position of the upper quartile will be accepted as  or .

Examples

1. From a stem and leaf:
   Use your diagram to find the median number of people on a bus.

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