Statistical Landmarks

Statistics - collecting, organizing, analyzing and presenting data.

Data – pieces of information that are often numerical.

When we count, measure, ask questions, observe and describe, the information we collect is called data.

For example, let’s collect the month that each member of a baseball team was born. There are 9 players. The months are:

8, 2, 5, 7, 2, 10, 4, 5, 1

Landmarks are used to describe the set of data:

The minimum is the smallest value of the data.

The maximum is the largest value of the data.

The range is the difference between the minimum and the maximum.

The mode is the value(s) that occurs most often.

The median is the middle value (not the average).

To find the median, arrange the numbers from smallest to largest. Then, start crossing the numbers off from each end of that list.

1 2 2 4 5 5 7 9 10

Average - a number that helps describe all of the data in a data set – also known as a measure of central tendency.

One of the most common measures of central tendency is:

The mean - the average value.

To find the average, add up all the numbers and divide that answer by the number of numbers. In our example, the sum of all 9 numbers is: 45. Then divide 45 by 9. The mean is: 5

In our example:

Minimum	1
Maximum	10
Range	9
Mode	2,5
Median	5
Mean	5

Note: The mean and the median are not always the same !!!

Outlier – a value in a set of data that is much higher or much lower than the other values in the same data set. An outlier can significantly affect the mean of the data set.