# Levels of data, Central tendency & measures of dispersion

What is nominal data?
Nominal data simply tells us the number of people/things falling into certain catagories, eg- the number of A level students doing Maths.
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How is nominal data normally presented?
Bar chart
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What is Ordinal data?
Allows us to put things in order eg- top 3 in a race. However we can't tell the difference between the data, like how close runner 1 and 2 were together
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What is interval and ratio data?
Allows us to put things in order and know the size of the gaps between. Usually a piece of technical equipment is needed.
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What is the difference between interval and ratio data?
Ratio data has a true zero eg- weight, as weight can't drop below zero grams. Interval data doesn't have a true zero, eg- temperature.
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What are the good points of using a mean to calculate average?
It's data sensitive, it uses all the values
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What are the bad points of using mean to calculate average?
It can be affected badly by outliers, so the value calculated may not be central.
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What are the good points about using the median to calculate average?
It doesn't get affected by outliers easily
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What are the bad points of using the median to calculate average?
It ignores most of the data we've collected and can be fairly time consuming to place all the data in order.
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What are the good points of using the mode to calculate average?
Its easy to calculate, can be better if data is not suitable to be shown in decimals, eg- number of children per household
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What are the bad points of using the mode to calculate average?
the mode might not be the central number.
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What are the positives and negatives of using the range to calculate dispersion?
Easy to calculate, however doesn't consider all the data and is very prone to outliers!
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What are the positives and negatives of using Standard Deviation to calculate Dispersion?
It uses all the data, the smaller the standard deviation the closer our data is to our mean
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## Other cards in this set

### Card 2

#### Front

How is nominal data normally presented?

Bar chart

### Card 3

#### Front

What is Ordinal data?

### Card 4

#### Front

What is interval and ratio data?

### Card 5

#### Front

What is the difference between interval and ratio data?