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#### Statistics

###### Histograms
• • A histogram displays the frequency of either continuous or grouped discrete data in the form of bars.
• The bars are joined together.
• The bars can be of varying width.
• The frequency of the data is represented by the area of the bar and not the height.
• When class intervals are different, it is the area of the bar which represents the frequency, not the height.
• Instead of frequency being plotted on the vertical axis, frequency density is plotted.
• Class width = Interval
• Frequency density = Height
• Frequency = Class width × Frequency density
###### Averages
• Mean: • Median:
• is the middle value when the data has been written in ascending or descending order.
• For an even number of values: add the two numbers in the middle and divide by 2.
• Mode: is the most frequently occurring value
• Range: is the difference between the highest and lowest values.
• Estimated mean of grouped data:
• Work out the midpoints of each group and multiply by the frequency.
• Then divide by the number of values.
###### Cumulative Frequency
• Cumulative frequency is the total frequency up to a given point.
• Inter-quartile range = upper quartile – lower quartile. Minimum 4 characters