StatisticsLesson 1 of 1 in the course Descriptive Statistics

Constructing and Interpreting Box Plots: Quartiles, Spread, and Whiskers

5 flashcards · 5 quiz questions · 5 match pairs · 4 fill-in sentences · English

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Summary

A box plot turns a data set’s five-number summary into a compact visual display. It helps you see the center and overall spread of the data at a glance.

Together, these values are called the five-number summary. The interval from Q1Q_1 to Q3Q_3 contains approximately the middle 50% of the data.

Definition: A box plot, also called a box-and-whisker plot, is a graph based on the minimum, Q1Q_1, median, Q3Q_3, and maximum of a data set.

All flashcards

Five-number summary
The minimum, Q1Q_1, median, Q3Q_3, and maximum of a data set.
Interquartile range (IQR)
The spread of the middle 50% of the data, calculated as Q3−Q1Q_3-Q_1.
Box plot whiskers
Lines extending from the box toward data extremes; some plots instead mark outliers separately.
Scaled number line
A number line that places values at proportional distances when constructing a box plot.
Coincident summary values
When two summary values are equal, their marks occupy the same position on the plot.

Quiz questions

  1. A data set has a minimum of 59 inches and a maximum of 77 inches. What is its range?Answer: 18 inches
  2. For a data set with Q1=64.5Q_1=64.5 and Q3=70Q_3=70, what is the interquartile range?Answer: 5.5
  3. In a box plot that marks outliers as separate dots, what might the whiskers represent?Answer: They may stop short of the minimum and maximum.
  4. When two groups are shown on the same scale, what does a wider box indicate?Answer: A larger interquartile range
  5. When two box plots use a common scale, what does a box positioned farther to the right generally indicate?Answer: Higher data values

Based on Introductory Statistics 2e by Barbara Illowsky, Susan Dean (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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