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STA 111 lesson
Grouped quantiles and spread
Use grouped quantiles and spread to solve and interpret a specified problem.
Source note: corrected against the supplied pages.
STA111-T09-L02; Source: T25-28 | Course topic 9
For grouped data, estimate percentile p by L+[(pN-C)/f]h, using the class containing pN. IQR = Q3-Q1 and semi-IQR = IQR/2. Quantiles are in the original measurement units. Cumulative percentages and an ogive can be used for approximate graphical readings. The grouping approximation assumes observations are sufficiently spread through the relevant interval for linear interpolation to be reasonable.