Describing the Distribution of Data

Graphing Data

When data is graphed, we can see the shape or distribution of the overall responses.

Bell Curve

Some data will form a bell curve when it is graphed.  (The overall shape looks like a bell.)  In this type of shape, most of the responses cluster around the center.  They taper off at either end. 

The mean is at the center of the bell curve.  Half of the data is distributed to the right and half of the data is distributed to the left.

Example

The line plot below is a visual representation of data.  It shows the shoe sizes for a group of students in middle school.

The overall distribution of the data could be described as a bell curve.

Skewed Data

Skewed data has a spread of data, or a "long tail," to one side or the other.

Negative Skew

A negative skew has a long tail to the left.

Positive Skew

A positive skew has a long tail to the right.

Practice

Label each graph below as either bell curve, right-skewed, or left-skewed.

1. 

2. 

3. 

Answer Key

1.  left-skewed

2.  bell curve

3.  right-skewed