Position and shape of distributions
Interpret position, spread, and outliers using quartiles and box plots.
Meaning
Quartiles mark divisions of sorted data into four parts. The interquartile range is the third quartile minus the first. A box plot summarizes the middle portion, spread, and asymmetry.
Example
If the first quartile is 10, the median is 14, and the third quartile is 18, approximately the middle half of the data lies from 10 to 18. The interquartile range is 8. Quartile conventions can differ for small data sets. Meeting an outlier criterion alone does not establish that an observation is erroneous or should be deleted.
Practice for this concept
Scope and references
Topics
Quartiles, interquartile range, box plots, outliers
Learning goal
Interpret position, spread, and outliers using quartiles and box plots.
Helpful background
Sort the data and examine its median and spread.
Distribution position and shape
These choice exercises calculate or judge specified finite data, trials, or assumptions. They do not establish data collection, written inference, model validation, or mastery of the whole statistics area.