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GCSE Statistics · key term
A boundary in an ordered distribution expressed as a percentage position. The pth percentile, , marks approximately the lowest p% of the data.
Used by Edexcel
Specification 2c.01, 2c.04 · Paper 1, Paper 2
Revise: Calculating measures of spreadPercentiles describe boundaries in hundredths rather than quarters.
A boundary value in ordered data corresponding to a specified percentage of the observations. For example, the 90th percentile marks the boundary below which approximately 90% of observations lie.
Put raw data in ascending order before finding quartiles or percentiles. Distinguish a position in the ordered list from the value at that position.
Subtract the lower boundary value from the upper boundary value, not their percentile numbers. Give measures of spread in the original data units.
Compare the same measure for both data sets, using the same units. For an interpercentile range, use the same percentile boundaries.
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