Intro

- Measures of location are a form of numerical representation of data
- They’re basically just averages
- You’ve got the mean, the median and the mode
- I’m sure you know what they are, if you’ve made it as far as A-Level Maths
- I’ll cover finding them from charts / diagrams in a different post

The Mode

- The mode is pretty easy to calculate
- Calculate? You just count to find out which one occurs the most!
- There could be no mode, or there could be several modes
- It’s not affected by anomalously extreme values
- It works for both qualitative and quantitative data
- Unfortunately, it’s got no useful mathematical purposes

The Median

- The median is also not affected by extreme values
- It’s still not as useful as the mean
- It’s easy to find from raw data – you just look for the middle one
- (If there’s an odd number of numbers, there will be an obvious middle number. If it’s an even number of numbers, you’ll have to go half way between the two middle numbers – unless the two middle numbers are identical, which would be nice)
- Finding it from group data is trickier, though…

The Mean

- It uses all the values in the data set
- Unfortunately, that means extreme values can distort it
- Its uses include being part of the standard deviation and standardizing normal distributions…
- Add all the data and divide by the number of items of data – you know the drill
- The formula for the mean can be
~~written as~~pronounced “x bar equals sigma x over n”, where x bar is the letter x with a horizontal line over it, sigma is that Greek letter that looks a bit like a capital E, and means “the sum of”, and n is the letter n, representing the number of items of data in the data set.

I’d draw it for you, but I don’t have a graphics tablet on me…

###### Related articles

- Measures of Location – AS Maths Revision – Statistics (S1) (mattg99.wordpress.com)
- Averages from Charts / Tables – AS Maths Revision – Statistics (S1) (mattg99.wordpress.com)
- Skew, Box Plots and Outilers – AS Maths Revision – Statistics (S1) (mattg99.wordpress.com)
- ‘Coding’ and Measures of Dispersion – AS Maths Revision – Statistics (S1) (mattg99.wordpress.com)
- Statistical Models, Data, Classes – AS Maths Revision – Statistics (S1) (mattg99.wordpress.com)

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