Stats GCSE Averages+comparing data sets

Pro’s of using the mode

Pro’s of using the mode

Easy to find, can be used with qualitative and quantitative data, unaffected by extreme values, always a value in the data

What’s the mode?

The most common value

Con’s of using the mode

Might be no mode or more than one mode, can’t be used to calculate measures of spread

Pro’s of using the median

Easy to calculate, unaffected by outliers, best to use with skewed data

What’s the median

The middle value

Con’s of using the median

May not be a value in the set of data

Pro’s of using the mean

Uses all the data, can be used to calculate standard deviation and skew

What’s the mean

The sum of the values divided by the number of values

Con’s of using the mean

May not be a value in the set of data, always affected by extreme values, can be distorted by open-ended classes

How to calculate an outlier

<LQ-(1.5\*IQR)

>UQ+(1.5\*IQR)

What’s the standard deviation

How much the individual values differ from the mean

How to calculate skew

(3*(mean-median))/standard deviation

How do you compare data sets?

Using a measure of average, spread or skewness

How do you compare averages?

… for data A is larger than … for data B, so on average data A is more …

How do you compare spread?

… for data A is larger than that of data B so data A is less consistent than data B

What does a positive skew mean?

Majority of results were low with few higher results

What does negative skew mean?

Majority of results were high with few lower results