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Types of data
- Categorical: Ordinal, nominal
- Numerical: Discrete, continuous
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Categorical
A category is recorded when the data is collected.
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Numerical
- When data is collected a number is recorded. There are two types
- Discrete: The numbers are distinct values, often whole numbers and usually the data comess from counting.
- Continuous: Any number on a continuous number line is recoded; usally the data is produced by measuring to any desired level of accuracy.
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Bar chart
Categorical data
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Mode
The most frequently occuring value or category.
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Segmented bar chart & Percentage segmented bar chart
Categorical data
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Histogram
- Continuous data
- Columns are joined together
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Column graph
- Discrete data
- Equal width with spaces between
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Symmetrical
Same shape either side of the centre
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Positively skewed
Tails off to the right
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Negatively skewed
Tails off to the right
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Outliers
Extreme values, well away from the majority of data, should be considered.
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Range
largest value - smallest value
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Median
- O2
- The middle value when the data is ordered
- (n+1/2)
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The interquartile range
- IQR
- Q3 - Q1
- Q3= the midpoint of the upper half
- Q1= the midpoint of the lower half
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Mean
- αΊ‹
- The average
- mean= sum of data values/ total number of data values
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68%
one standard deviation of the mean
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