Maths Statistics

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Histograms- no gaps, find lower + upper boundary and class width.

Frequency density = frequency / class width

area of each bar = frequency

Stem and Leaf diagram - remember a key

Cumulative Frequency graphs - show upper class boundary and cumulative freq.

cumulative freq = y axis, upper boundaries = x axis

median = 0.5(Ecf+1) on y axis and then read across, 0.25 for lb, 0.75 for ub.

Percentiles - divide data into 100, Pn = N/100 x (total freq + 1) , where n = position

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Box and whisker diagrams - always draw a scale

Variance = Efx2/Ef - mean2 or Ex2/n - mean2

Standard deviation = ?/variance

For grouped data, assume every reading takes the mid-class value

Coding - y = x-b/a, My = Mx-b/a, Sy = Sx/a , where M is mean of

Skewness, PCS = 3(mean- median)/std. dev. lies between -3 and 3, with -3 as negatively skewed

Quartile skewness = Q3-2Q2+Q1/Q3-Q1

Outliers fall outside fences- method will be given in Q

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