What is the Mean in a Data Set?
You will see at least one question on your entrance exam that asks: What is the mean?
To find the mean in a data set, you must add up all of the values in the set, and then divide by the amount of items in the set.
The mean is sometimes referred to as the arithmetic mean or the average.
Exam questions asking you to find the mean will provide the data in narrative form or in charts or tables.
For example, consider the following data set: 10, 11, 14, 12, 15
The mean for this data set is calculated as shown below.
STEP 1: Find the total of the values.
10 + 11 + 14 + 12 + 15 = 62
STEP 2: Divide the total from step 1 by the amount of items in the set to find the mean.
Here we have 5 numbers in the set.
62 ÷ 5 = 12.4
So, the mean is 12.4.
The mean should not be confused with the median or the mode.
What is the Mean If the Data Set Changes?
If one or more values is removed from or added to your data set, you will need to recalculate the mean.
If you add a value greater than the mean, the mean will increase.
On the other hand, the mean will decrease if you add a value that is less than the existing mean.
The mean will increase if you remove a value from the data set that is less than the mean.
However, the mean will decrease if you remove a value that is greater than the mean.
What is the Mean If Items Are Weighted?
You may see problems that state that certain items in a mean calculation carry more weight than others.
For example, your grade for a class may be determined by taking the average of your project scores by 25% and the average of your test scores by 75%.
So, if you received an average score of 70 on your projects and an average score of 80 on your exams, your grade is calculated as follows:
(70 × .25) + (80 × .75) = 17.50 + 60 = 77.50
Exam questions may also ask you how to correct an erroneous mean calculation.
You may also want to try our other free statistics exercises.