Statistics

Quantitative variables = numerical observations

Qualitative variables = non-numberical observations

Discrete variable = specific values in a given range

Continuous variable = any value in a given range

Mode = value that occurs most often

Median

middle value when the data is put in order

(n+1)/2 gives the place of the median value

Mean

Sum of all observations divided by the total number of observations

∑x/n

Mean

∑fx/∑f

To find the mean and median its helpful to add a column for the cumulative frequency

Grouped data

in grouped data x = the midpoint

modal class = class with highest frequency

Interpolation must be used

a/b=c/d

(see page 21 in edexcel)

Range = difference between highesh and lowest value

Quartiles = split data in to four parts eg. lower quartile (Q1) = n/4

Interquartile range = Q3-Q1

Percentiles = split data in to 100 patys

xth percentile = Px = xn/100