Mean, Median, Mode, Range & Stem and Leaf

Plots

Measures of Central Tendency

MeanThe mean is the Average of a

group of numbersIt is helpful to know the

mean because then you can see which numbers are above and below the mean

Mean ExampleHere is an example test scores for Ms. Math’s class.

82 93 86 97 82To find the Mean, first you must add up all

of the numbers.82+93+86+97+82= 440

Now, since there are 5 test scores, we will next divide the sum by 5.

440÷5= 88The Mean is 88!

Another Mean ExampleHere is an example test scores for your math class.

72 93 86 97 x – test you haven’t taken yet

What if you wanted to get at an 85 in your math class for your final grade. What is the lowest you can make on the test you haven’t taken

yet? How would you figure it out? Let’s see if we write and solve this out.X =

77

MedianThe Median is the middle

value on the list.The first step is always to put

the numbers in order from least to greatest.

Median Example First, let’s examine these five test scores.

78 93 86 97 79

We need to put them in order.78 79 86 93 97

The number in the middle is 8678 79 86 93 97

In this case, the Median is 86!

Median Example #2Now, let’s try it with an even number of test scores.

92 86 94 83 72 88

First, we will put them in order72 83 86 88 92 94

This time, there are two numbers in the middle, 86 and 8872 83 86 88 92 94

Now we will need to find the Average of these two numbers, by adding them and dividing by two.

86+88= 174 174÷2= 87

Here the Median is 87

ModeThe Mode refers to the number that

occurs the most frequently.It’s easy to remember… the first two

numbers are the same! MOde and MOst Frequently!

Mode ExampleHere is an list of temperatures for one

week.Mon. Tues. Wed. Thurs. Fri. Sat.

Sun. 77° 79° 83° 77° 83° 77°

82°

Again, We will put them in order.77° 77° 77° 79° 82° 83° 83°

77° is the most frequent number, so the mode= 77°

RangeThe range is the difference between

the highest and the lowest numbers of the series.

All we have to do is find the highest number and the lowest number and subtract!

Range ExampleLet’s look at the temperatures again.

77° 77° 77° 79° 82° 83° 83°

The highest number is 83, and the lowest is 77.

All you need to do is subtract!83-77= 6

In this case, the Range is 6

Stem and Leaf PlotsThis a way to display data in an

organized manner.

0 2 4 51 3 6 7 8 82 0 2 3 7 9

What numbers does this stem and leaf plot represent?

Stem and Leaf PlotsCan you find the mean, median,

mode, and range of the stem and leaf plot?

0 2 4 51 3 6 7 8 82 0 2 3 7 9

Stem and Leaf Plot Numbers:2, 4, 5, 13, 16, 17, 18, 18,20, 22, 23, 27, 29

Now YOU try it!!!This is the AVERAGE Family!

Dad Mom Jack Alex Katie

34 33 5 4 1

The Average Family

Make a stem and leaf plot of the family’s ages.

Dad Mom Jack Alex Katie 34 33 5 4 1

MeanHere are the ages again…Dad- 34, Mom- 33, Jack- 5, Alex- 4, Katie-

1

What is the Mean?

Remember… Mean is the AVERAGE

MeanRemember, to find the mean, we have to first

add up all of the numbers.

34+33+5+4+1= 77

Then, since there are 5 people in the family, we next divide by 5.

77÷5= 15.4

The Mean in this case is 15.4

MedianHere are the ages again…Dad- 34, Mom- 33, Jack- 5, Alex- 4, Katie-

1

What is the Median?

Remember… Median is the MIDDLE NUMBER

MedianRemember, to find the mean, we have to

first put all of the numbers in order.

34 33 5 4 1

The Mean in this case is 5

ModeHere are the ages again…Dad- 34, Mom- 33, Jack- 5, Alex- 4, Katie-

1

What is the Mode?

Remember… Mode is the MOST FREQUENT

ModeRemember, to find the mode, we have

to first put all of the numbers in order.

34 33 5 4 1

The Mode, in this case, does not exist. Since there is not a number that appears most often, you write no

mode.

RangeHere are the ages again…Dad- 34, Mom- 33, Jack- 5, Alex- 4, Katie-

1

What is the Range?

Remember… Range is the DIFFERENCE

RangeRemember, to find the range, we have to

first put all of the numbers in order.

34 33 5 4 1

The highest age is 34, and the lowest is 1

Now we need to subtract to find the difference

34-1= 33

The range is 33

Now let’s see how you do on yesterday and today’s

concepts…

Pg. 62 & 63 2-22, 30-34 evens only

AND

Pg. 121 6, 8, 20-22, 25 all problems