1. Which set of batteries would you buy?1 2 3 4 5 6 7 8 9 10 11 12
Range for Energizer : Highest – Lowest = 8 – 6 = 2
Range for Duracell : Highest – Lowest = 10 – 3 = 7 1 2 3 4 5 6 7 8 9 10 11 12

2. Range = Highest – Lowest
The RANGE of a data set
The Range of a data set is found by finding the difference between the highest and lowest values in the data set:
Range = Highest – Lowest
It shows how spread out data is and most often a smaller range means a better result 

3. L.O. To be able to identify which average is the best in a given situation
By the end of the lesson we will be able to:
identify what we mean by the best average
read a situation and choose the best average
read a situation and say why an average may give a bad representation of the data

4. Which average to choose?
The following data represents the pocket money given to kids by their guardians per week
€10, €16, €13, €12, €10, €100, €14
What is the mean ?
What is the mode?
What is the median?
Do you think the MEAN represents the data well?
What would be a better average?
€25
€10
Mention outlier .
€13

5. Number of parcels from each job:
Leona the Lorry Driver
Leona picks up lots of packages to deliver to each of her customers.
She wants to know the modal number of parcels she picks up from each job in order to do her monthly report.
Number of parcels from each job:
12, 9, 6, 7, 9, 12, 9, 10, 5, 6, 12, 6
Can you see why Leona could be confused this month?
What should she do?

6. Harold the Hairdresser
Harold can only afford to replace one blade from his hair-clipping set
He records the most asked for blades from his last 10 customers
His last 10 customers requested: 1,2,3,1,1,1,4,2,3,1,1
Based on the responses, which average should he use to make his decision?

7. Calculate the mean, mode, median and range of these amounts.
1) This list shows the amounts spent by 7 families on their holiday: €100, €400, €320, €300, €5430, €100, €350.
Calculate the mean, mode, median and range of these amounts.
b) Suggest which of the three averages is the most useful indicator of how much a typical family spends on their holiday.

8. 2) List of sizes sold 7, 8, 8, 8, 8, 9, 9, 10, 10, 11, 11
A sports shop is offering a discount on a particular type of running shoe.
The manager wants to look at the number of each size sold so far in order to predict how many will be sold in the next week.
a) Calculate the mean, mode, and median of the data.
b) Which of the three averages is most useful to the manager?

9. Summary
The MEAN gives a good representation of the data, when the data has a SMALL RANGE!
The MEDIAN is better than the MEAN when the data has a BIG RANGE!
The MODE is not useful if there are no modes or more than one mode
The MODE is the best average, when the aim is to identify the most popular item

10. What are the pros and cons of each average?
Mean
Median
Mode
Includes every value in the calculation
Affected by ‘extreme’ values
Isn’t affected by ‘extreme’ values
Doesn’t include all the data
Isn’t affected by ‘extreme’ values
Only average that can be used with words
No use if all the data is different
No use if there is more than one mode