WHAT DO THEY ALL MEAN?

4 ways to describe dataThe Mean – The average number in a data set.

The Median – The middle number in a data set…..50% of the numbers are above and 50% are below the median

The Mode – The number that occurs most often. (Most popular)

The Range – The difference between the maximum and minimum number.

MEASURE OF MEASURE OF CENTRAL TENDANCYCENTRAL TENDANCYA number that helps describe where the middle of a group of data lies.The mean, median, and mode are measures of central tendancy.

This is what we usually mean when we say “What’s my average?”

My MEAN old teacher calculates my AVERAGE!

Mean

Finding The Mean

• Add all the numbers in the set together.

• Divide the sum by the number of data items in the set.

• The quotient is the mean of the set of numbers.

• My test grades are: 100, 88, 92 and 84

• Add 100 + 88 + 92 + 84 = 364• Divide 364 by 4

– The mean is 91

Your grades on five tests:

95, 87, 92, 100, and 85

Put them in order from least to greatest

85, 87, 92, 95, 100

The middle number is the median

Your median test grade is 92 – half the time you score below 92 and half the time below 92

Finding The Median

Your grades on six tests:

95, 87, 92, 100, and 94

Put them in order from least to greatest

85, 87, 92, 94, 95, 100

The middle is between 2 numbers

The median is the mean of 92 and 94

Or

92 + 94 = 186

186 divided by 2 = 93

Finding The Mode

The number in a data set that occurs most often

Your grades: 95, 87, 85, 100, 100

Arrange the set of numbers from least to greatest85, 87, 95, 100, 100

Your mode is 100

You don’t have to have a mode…….

Some data sets have no mode or no number that occurs more than others

Some might have two modes

Another way to describe data

Asks the Question:

How spread out is my data?

Finding The Range

• Back to your test scores:• 100, 88, 92, and 84• Arrange the numbers in the set in order from least to

greatest.• 84, 88, 92, 100

• Your maximum score is a 100

• Your minimum score is 84

• Your range is 100 – 84 = 16

• The range = 16 or 84-100

It’s Time To Practice!Number of pets owned by 7 students:

2, 1, 1, 4, 3, 2, 1

What is the mean 2

What is the median 2

What is the Mode 1

What is the Range 3