Chapter 10

10.1 calculating statistics

>  you can use statistics to summarise sets of data.

>  yo can also use them to compare different sets of data.

you should be able to calculate three different sets of data: the mode, the median, and the mean.

{ mode = most common value or number }

{ median = middle value *when they are listed in order }

{ mean = the sum of all the values divided by the number of values }

{ range = the largest value minus the smallest }

* is not an average

EXAMPLE

QUESTION

Number of beads/25 /30 /35 /40 /45 /50

frequency           /34 /48 /61 /30 /15 /12

the table shows the number of beads on 200 necklaces

A. find the mode

B. find the mean

C. find the range

ANSWER

A. the mode is 35 ( the mode is the number with the highest frequency)

B. 6900 : 200 = 34.5

C. 50 - 25 = 25

10.2 Using statistics

You have to decide which average to use to work out several different statistical measures.

choose mode --> if you want to know which is the most commonly occuring number.
median --> is the middle value, when the data values are put in order.
mean--> depends on every value, if you change one number you change the mean.

EXAMPLE

QUESTION

Here are the ages, in years, of the players in a football team.
work out the average age.give a reason for your choice of average.

16, 17, 18, 18, 19, 20, 20, 21, 21, 32, 41

ANSWER

The mode is not a good choice

the mean will be affected by the two oldest people.

the median is 20 and this is the best average to use in this case.