Centre & Spread
Name the three terms for calculating the 'average' or centre of a data set
Mean, median and mode
Name a measure of spread
Range
What measure of centre is most appropriate for when there are no outliers in the data?
Mean or median
How do you calculate the mean?
Sum of all the values divided by the total number of values
How do you calculate the range?
Range = the highest number - the lowest number
What is the definition of an outlier?
An outlier is a data point that is significantly smaller or larger than the rest of the data.
What are the steps for working out the median?
First put the numbers in ascending order, then select the middle number. If there are two middle numbers you will need to find the mean of the two numbers to calculate the median.
What is the mode of this data set:
2 5 7 9 11 15 6 8 23 27 34 1 0 89
There is no mode because they all repeat once.
What can an outlier effect?
Outliers can affect the overall measures from a group of data, particularly the mean and range.
Give a full description of the mode
The mode is the most common value, i.e. the one with the highest frequency. There can be more than one mode.
What is the range of the set of scores below? Show full working on the board.
7 5 1 6 7 5 7 10 7 6
Range = highest number - lowest number
Highest number = 10
Lowest number = 1
10 - 1 = 9
Range = 9
Identify the outlier in the data set below and state what measure of centre would remain unchanged by the outlier?
20, 17, 19, 22, 18, 17, 5
Outlier = 5
The MODE would remain unchanged.
What is the mean of this data set:
2 5 7 9 11 15 6 8 23 27 34 1 0 89
237 / 14 = 16.93
What is the median of this data set:
3 5 2 6 7 4
Put into ascending order: 2 3 4 5 6 7
Find the 2 middle values: 4 and 5
Find the average of those scores: (4 + 5) / 2
Median = 4.5
Identify the outlier and calculate the mean with and without the outlier for the below data set:
3, 2, 6, 4, 3, 5, 16
Outlier = 16
Mean with Outlier = 5.6
Mean without the Outlier = 3.8