StatisticsLesson 2 of 5 in the course Descriptive Statistics

Constructing Histograms, Frequency Polygons, and Time-Series Graphs

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

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Summary

Histograms provide a clear visual summary of how numerical data are distributed. They are especially useful when a data set is large and you want to see its overall shape.

A histogram displays numerical data by grouping values into intervals, also called classes. Each class is represented by a bar, and the bars touch because the intervals are adjoining. The horizontal axis identifies the data values or intervals; the vertical axis shows the frequency, relative frequency, percent frequency, or probability for each interval.

All flashcards

What is a histogram?
A graph that groups numerical data into adjoining class intervals and displays the frequency or proportion in each interval.
What does frequency mean?
The number of observations that occur in a value or class interval.
How do you calculate relative frequency?
Divide the frequency for a class, ff, by the total number of observations, nn: RF=f/nRF = f/n.
What can a histogram help describe?
The shape, center, and spread of a numerical data distribution.
Why do histogram bars adjoin?
Each bar represents a class interval, and the intervals are next to one another.

Quiz questions

  1. In a frequency polygon, what does the horizontal coordinate of each plotted point represent?Answer: The midpoint of a class interval.
  2. Why are zero-frequency classes added at both ends of a frequency polygon?Answer: They allow the line to meet the horizontal axis at both ends.
  3. Which axis represents time in a standard time-series graph?Answer: The horizontal axis.
  4. What key information is preserved by plotting time-series observations in chronological order?Answer: The sequence in which measurements occurred.
  5. How can a narrow vertical axis range affect the appearance of a time-series graph?Answer: It can make a modest change appear more dramatic.

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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