The mode is a measure of central tendency. In other words, it's one way of describing a value that represents the middle or the centre of a data set so we get a sense of what is "normal." The mode describes the most frequently occurring score. Remember the word and the meaning start with the same two letters.

Let's say I asked $10$10 people how many pets they had and $2$2 people said no pets, $6$6 people had one pet and $2$2 people said they had two pets. What is the most common number of pets for people to have? The answer is one pet because the majority of people $\frac{6}{10}$610 had one pet. So the mode in this data set is $1$1.

The mode is the most common score. So if we add or subtract a score, the mode may, but does not always, change. We just need to check which score occurs most often if the data set changes.

Example

Question 3

Assess how various changes to data sets alter their characteristics.

a. Consider the set of data: $1,2,2,4,4,5,6,6,8,9$1,2,2,4,4,5,6,6,8,9

If the score of $8$8 is changed to a $9$9, how would the mode be affected?

Think: What was the mode when the score was an $8$8? What was the mode when the score was changed to a $9$9?

Do:

The mode when the score was an $8$8 was $2$2, $4$4 and $6$6 as all these scores occur twice. The mode changed when the score was changed to a $9$9 as now $2$2, $4$4, $6$6 and $9$9 all occur twice.