Statistics Formulae and key words 3.5 / 5 StatisticsASEdexcel Created by: NiaCreated on: 09-04-12 11:56 Variables 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 1 of 5 Mean, mode and median in a set of data 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 2 of 5 Mean, mode in frequency distribution tables and gr 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 3 of 5 Median in grouped data Interpolation must be used a/b=c/d (see page 21 in edexcel) 4 of 5 Quartiles and range and percentiles 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 5 of 5

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