Accuracy and Precision
Accuracy and Precision

Accuracy and Precision

Author: Nathan Lampson
This lesson will explain the difference between accuracy and precision.
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Introduction to Psychology

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Three different scientists are given thermometers to measure the temperature outside five times.  The actual temperature outside is 73 degrees fahrenheit for all five readings.  The graph for the actual temperature outside would look like this.

The first scientist takes 5 readings and all five readings are the same, 47 degrees.  The first scientist's readings were very far from the actual temperature of 73 degrees, however, they were very consistent.


Precision is the word used to describe data that is very consistent and repeatable. If the first scientists were to take a 6th temperature reading, they would likely find a temperature of 47 degrees.  The data is very repeatable.

The second scientist took their 5 readings and the graph can be viewed below.  Their 5 temperature readings were 83, 63, 83, 63, and 83 degrees F.  The second scientist's readings were not very precise, however, they were closer to the actual temperature of 73 degrees than the first scientist.


Accuracy is a measurement of how close to the actual value a data point is.  If the actual temperature is 73 degrees, a value of 70 is more accurate than a value of 47.