Graphs organize data so patterns and comparisons are easier to see. This lesson introduces three graph types: stem-and-leaf graphs (stemplots), line graphs, and bar graphs. Each is suited to a different purpose.
A stemplot divides each numerical observation into a stem and a leaf. The leaf is usually the final significant digit; the remaining digit or digits form the stem. For example, for 23 the stem is 2 and the leaf is 3; for 432 the stem is 43 and the leaf is 2. For a decimal such as 9.3, the stem is 9 and the leaf is 3.
All flashcards
What is a stemplot?
A graph that splits each numerical observation into a stem and a leaf, listing stems vertically and ordering leaves beside their matching stems. It displays the distribution while retaining the individual data values.
What does a leaf usually represent?
The leaf is usually the final significant digit of an observation. For example, in 432 the leaf is 2 and the stem is 43.
How is a line graph of frequencies organized?
Data values are placed on the horizontal x-axis and their frequencies on the vertical y-axis. The value-frequency points are connected with line segments.
What does the separation between bars communicate?
Each bar represents a distinct category or group, and the gaps emphasize that the categories are separate rather than continuous.
What is an outlier, and how should it be interpreted?
An outlier is an observation that does not fit the general pattern of the other data. It may be an error or a genuine unusual value, so context should be considered before deciding what it means.
Quiz questions
In a stemplot, what values are represented by the row 4 | 2 9 9?Answer: The values 42, 49, and 49.
A frequency table lists frequencies of 2, 5, 8, 14, 7, and 4 for six ordered data values. At which value is the line graph's highest point?Answer: At the fourth data value.
Why are bars separated in a bar graph?Answer: The gaps indicate that the bars represent distinct categories.
Most supermarket distances are between 1.1 km and 6.7 km, but one distance is 12.3 km. What is the most appropriate interpretation?Answer: The 12.3 km value may be an outlier; context is needed to interpret it.
A survey records how many times per week parents remind teenagers to do chores. The frequencies for 0 through 5 reminders are 2, 5, 8, 14, 7, and 4. How many parents were surveyed?Answer: 40 parents.
Based on Introductory Statistics 2e by Barbara Illowsky, Susan Dean (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.