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Mean, Median, Mode
To practice more, or to go for more help, then try some of
these websites!http://www.bbc.co.uk/schools/revisewise/
maths/data/12_act.shtmlhttp://www.mathgoodies.com/lessons/toc
_vol8.shtmhttp://math.about.com/library/weekly/aa0
20502a.htm
Definition
• Mean – the average of a group of numbers.
2, 5, 2, 1, 5Mean = 3
Mean is found by evening out the numbers
2, 5, 2, 1, 5
Copyright © 2000 by Monica Yuskaitis
Mean is found by evening out the numbers
2, 5, 2, 1, 5
Copyright © 2000 by Monica Yuskaitis
Mean is found by evening out the numbers
2, 5, 2, 1, 5mean = 3
Copyright © 2000 by Monica Yuskaitis
How to Find the Mean of a Group of Numbers
• Step 1 – Add all the numbers.
8, 10, 12, 18, 22, 26
8+10+12+18+22+26 = 96
Copyright © 2000 by Monica Yuskaitis
How to Find the Mean of a Group of Numbers
• Step 2 – Divide the sum by the number of addends.
8, 10, 12, 18, 22, 268+10+12+18+22+26 = 96
How many addends are there?
Copyright © 2000 by Monica Yuskaitis
How to Find the Mean of a Group of Numbers
• Step 2 – Divide the sum by the number of addends.
6)96 sum# of addends1
636
6
63
Copyright © 2000 by Monica Yuskaitis
How to Find the Mean of a Group of Numbers
The mean or average of these numbers is 16.
8, 10, 12, 18, 22, 26
Copyright © 2000 by Monica Yuskaitis
Definition
Medianis in theMiddle
Copyright © 2000 by Monica Yuskaitis
Definition
• Median – the middle number in a set of ordered numbers.
1, 3, 7, 10, 13Median = 7
Copyright © 2000 by Monica Yuskaitis
How to Find the Median in a Group of Numbers
• Step 1 – Arrange the numbers in order from least to greatest.
21, 18, 24, 19, 27
18, 19, 21, 24, 27
Copyright © 2000 by Monica Yuskaitis
How to Find the Median in a Group of Numbers
• Step 2 – Find the middle number.
21, 18, 24, 19, 27
18, 19, 21, 24, 27
Copyright © 2000 by Monica Yuskaitis
How to Find the Median in a Group of Numbers
• Step 2 – Find the middle number.
18, 19, 21, 24, 27
This is your median number.
Copyright © 2000 by Monica Yuskaitis
How to Find the Median in a Group of Numbers
• Step 3 – If there are two middle numbers, find the mean of these two numbers.
18, 19, 21, 25, 27, 28
Copyright © 2000 by Monica Yuskaitis
How to Find the Median in a Group of Numbers
• Step 3 – If there are two middle numbers, find the mean of these two numbers.
21+ 25 = 46
2) 46 23 median
Copyright © 2000 by Monica Yuskaitis
What is the median of these numbers?
16, 10, 7
10
7, 10, 16
Copyright © 2000 by Monica Yuskaitis
What is the median of these numbers?
29, 8, 4, 11, 19
114, 8, 11, 19, 29
Copyright © 2000 by Monica Yuskaitis
What is the median of these numbers?
31, 7, 2, 12, 14, 19
132, 7, 12, 14, 19, 31
12 + 14 = 26 2) 26
Copyright © 2000 by Monica Yuskaitis
What is the median of these numbers?
53, 5, 81, 67, 25, 78
6053 + 67 = 120 2) 120
5, 25, 53, 67, 78, 81
Copyright © 2000 by Monica Yuskaitis
Definition
Modeis the most
Popular
Copyright © 2000 by Monica Yuskaitis
Definition• A la mode – the most popular or that which is in fashion.
Baseball caps are a la mode today.
Copyright © 2000 by Monica Yuskaitis
Definition• Mode – the number that appears most frequently in a set of numbers.
1, 1, 3, 7, 10, 13Mode = 1
Copyright © 2000 by Monica Yuskaitis
How to Find the Mode in a Group of Numbers
• Step 1 – Arrange the numbers in order from least to greatest.
21, 18, 24, 19, 18 18, 18, 19, 21, 24
Copyright © 2000 by Monica Yuskaitis
How to Find the Mode in a Group of Numbers
• Step 2 – Find the number that is repeated the most.
21, 18, 24, 19, 18 18, 18, 19, 21, 24
Copyright © 2000 by Monica Yuskaitis
Which number is the mode?
29, 8, 4, 8, 19
84, 8, 8, 19, 29
Copyright © 2000 by Monica Yuskaitis
Which number is the mode?
1, 2, 2, 9, 9, 4, 9, 10
91, 2, 2, 4, 9, 9, 9, 10
Copyright © 2000 by Monica Yuskaitis
Which number is the mode?
22, 21, 27, 31, 21, 32
2121, 21, 22, 27, 31, 32
Now YOU try it!!!This is the Stat Family!
Dad Mom Jack Alex Katie
34 33 5 5 1
MeanHere are the ages again…Dad- 34, Mom- 33, Jack- 5, Alex- 5, Katie- 1
What is the Mean?
Remember… Mean is the AVERAGE
Try it on your paper and see what you come up with!
MeanRemember, to find the mean, we have to first add up all of the numbers.
34+33+5+5+1= 80
Then, since there are 6 people in the family, we next divide by 6.
78÷6= 13
The Mean in this case is 13
MedianHere are the ages again…Dad- 34, Mom- 33, Jack- 5, Alex- 5, Katie- 1
What is the Median?
Remember… Median is the MIDDLE NUMBER
Try it on your paper and see what you come up with!
MedianRemember, to find the mean, we have to first
put all of the numbers in order.
34 33 5 5 1
The Mean in this case is 5
ModeHere are the ages again…Dad- 34, Mom- 33, Jack- 5, Alex- 5, Katie- 1
What is the Mode?
Remember… Mode is the MOST FREQUENT
Try it on your paper and see what you come up with!
ModeRemember, to find the mode, we have to
first put all of the numbers in order.
34 33 5 5 1
The Mode in this case is 5
ความสัมพันธระหวาง คาเฉลี่ย มัธยฐาน ฐานนิยม
Mean = Median = Mode
ความสัมพันธระหวาง คาเฉล่ีย มัธยฐาน ฐานนิยม
ความสัมพันธระหวาง คาเฉล่ีย มัธยฐาน ฐานนิยม
Mean, Median, and Mode
• Sometimes you get very similar results with all three.
• Like when you have a normal distribution.
Values
Freq
uenc
y
-4 -2 0 2 4
0.0
0.1
0.2
0.3
Mean
• Usually the mean is preferred:– It uses all the scores (so it’s representative of the
entire data set).
– It’s used to compute the variance and SD.
– It’s good for inferential statistics.
– Note that you should have interval or ratio data to compute a mean.
Median
• Use the median when you have extreme scores or a skewed distribution.
V a lu e s
Frequen
cy
0 .0 0 .2 0 .4 0 .6 0 .8 1 .0
0.00.5
1.01.5
2.0
Median
• Use the median when you have extreme scores or a skewed distribution.
• EXAMPLE:
• X = 10, 11, 11, 11, 11, 12, 12, 13, 13, 100
• M = 20.3
• Median = 11.5
• Median represents most of the distribution best.
Median
• In psychology, you might encounter an open-ended distribution like this:
• N = 20
• Cannot compute a mean.
• Median = 1.5
• Use the median!
Number of Children
Frequency
5 or more 34 23 22 31 60 4
Median
• Use the median if you have ordinal data.
• Remember, the mean balances distance.
• With ordinal data you don’t have equal distances between data points.
Mode
• Use the mode if you have nominal data.
• EXAMPLE:
• Hair color: – 1= brown
– 2 = black
– 3 = blond
– 4 = red
Hair color Frequency4 23 42 51 7
N = 18
Mode
• If you have a discrete variable like number of children, you can compute a mean.
• In this case, means are fractional values that can’t really exist. EXAMPLE: “The average family has 2.5 kids.”
• The mode identifies the typical case: – “The typical family has 2 kids.”– “The modal age for spinal cord injury is 19.”
When to Use the Mean, Median, and Mode