Statistical Distribution
Overview
Statistical data has a distribution. The distribution gives us a better understanding of the data collected.
For example…
The graph below shows the distribution of science exam scores for Mr. Walker’s class. What information can you determine based on the data collected?
The graph shows us the spread, center, and median.
The spread is the range of data points, from least to greatest. In this example, the spread is from 73 – 98.
The center is a range of points where most of the data occurs. In this example, the center is represented by a rectangular box. The center ranges from 80 – 85. So, most people in Mr. Walker’s class scored between an 80 and 85 on the science test.
The median represents the midpoint of the data. In this example, the median is 84.
Let’s look at another example…
What information does the line plot give us about the distribution of data?
The line plot shows us the shape of the distribution. It also shows us if there are any outliers.
The shape can be symmetrical, meaning it’s even on both sides of the center. It can also be left-tailed or right-tailed. This example is right-tailed because the data thins out to the right, making it look like it has a tail.
An outlier is one point that is far away from the rest of the data points. In this example, 98 is an outlier because there are no other points near it.
A gap is a large space between two data points. In this example, there is a gap between 91 – 98.
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The box plot below shows the number of laps the students in Ms. Gamble’s class ran
during gym class. Use the graph to answer questions
The distribution is “?“
A. symmetrical
B. left-tailed
C. right-tailed
B. left-tailed
The tail stretches to the left (the data thins out to the left).
The center of the distribution is “?” laps.
A. 5 – 27
B. 5 – 30
C. 20 – 23
D. 20 – 25
D. 20 – 25
The rectangular box represents the center.
The spread of the distribution is “?” laps.
A. 5 – 27
B. 5 – 30
C. 20 – 23
D. 20 – 25
A. 5 – 27
The long, horizontal line represents the spread of data.
What is the data’s median value?
A. 5
B. 20
C. 23
D. 25
C. 23
The short, vertical line within the rectangular box shows the median.
What else can you determine from the graph?
Answers may vary
Answers may include: No student ran more than 27 laps.