1. Section 5.4
Mean
Mean (average) is the most commonly used measure ofcentral tendency
To calculate the average we know that we need to sumup all the data and then divide by the number of datavalues
Ex: Find the mean for the following values:
There are 8 terms
Get the sum by adding upall the terms
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Ex: Jason wrote 5 tests with the following scores.What score will he need for his next test to get anaverage of 73%?
Note: There are 6 terms
Find the sum of the first 5 terms
Cross multiply and findthe value of the missing mark
Jason needs 66% on his nexttest to get an average of 73%
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Median:
Median is the value that lies exactly in the middle ofwhen all the datas are arranged in ascending order.
To calculate the median we must first arrange thedata from smallest to biggest
Then, the value that is exactly in the middle is themedian.
If there are two numbers in the middle, we mustaverage of the two middle values to get the median.
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Ex: Find the median from the following set of values
Arrange the numbers fromthe least to the greatest
There are seven values andthe middle is the fourthvalue
Arrange the numbers fromthe least to the greatest
There are two terms in themiddle, get the average ofthe two to find the median
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Mode:
Mode is the most frequently occurring value in a dataset.
There may be more than one mode for a given data setif there is the same frequency of two or more numbers.
To find the mode choose the number that appears themost.
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Ex: Find the mode for each set
Optional: Arrange the numbersfrom the least to the greatest
12 appears 3 times, so themode is 12
Numbers 14 and 30 bothappear 3 times, so the modeis both 14 and 30
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Ex: The following table shows the quiz mark of 30 students.The quiz is out of 9. Find the measures of central tendenciesfor the following values:
Frequency: how many times thatvalue appeared
The MODE is the easiest to get:
Nine people got a mark of 8, so themode is 8
To find the MEDIAN, there are 30
values, the middle number will be
the 15th value.
Count from the bottom to find wherethe 15th value is
MEDIAN = 7
To find the MEAN, understand thatthere are 2 people getting 4’s, six people
getting 5’s, four people getting 6’s, andso on
Add up all 30 terms and then
divide it by 30
Average mark in the class is 6.766
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