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Types of data
 Categorical: Ordinal, nominal
 Numerical: Discrete, continuous

Categorical
A category is recorded when the data is collected.

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.

Bar chart
Categorical data

Mode
The most frequently occuring value or category.

Segmented bar chart & Percentage segmented bar chart
Categorical data

Histogram
 Continuous data
 Columns are joined together

Column graph
 Discrete data
 Equal width with spaces between

Symmetrical
Same shape either side of the centre

Positively skewed
Tails off to the right

Negatively skewed
Tails off to the right

Outliers
Extreme values, well away from the majority of data, should be considered.

Range
largest value  smallest value


Median
 O2
 The middle value when the data is ordered
 (n+1/2)

The interquartile range
 IQR
 Q3  Q1
 Q3= the midpoint of the upper half
 Q1= the midpoint of the lower half


Mean
 αΊ‹
 The average
 mean= sum of data values/ total number of data values

68%
one standard deviation of the mean



