Formula

• stratified sampling


  stratum size/population size x number in sample
• comparative pie charts


  R squared/ r squared = N/n
• geometric mean


  the mean of n numbers expressed as the n-th root of their product
• Outliers in boxplot


  Q1 - 1.5 x IQR (or) Q3 + 1.5 x IQR
• Outliers and Standard Deviation


  mean +/- 3 x standard deviation
• skew


  3(mean - median)/standard deviation
• seasonal variation at a point


  actual value - trend value
• Estimated Mean Seasonal Variation


  mean of all the seasonal variations for that season
• predicted value


  trend line value + estimated mean seasonal variation
• relative risk


  risk for those in group/ risk for those not in group
• conditional probability


  P(B|A) = P(A and B) / P(A)
• index


  year n/base year x 100
• crude rate


  number/population x 1000
• standard population


  Number in Age Group / Total Population x 1000
• standardised rate


  crude rate/1000 x standard population
• normal distribution


  68%, 95%, 99.7%
• standardised scores


  (value-mean)/standard deviation
• quality assurance and control charts - warning limits


  target mean +/- 2 x standard deviation
• quality assurance and control charts - action limits


  target mean +/- 3 x standard deviation
• binomial distribution notation


  B(n,p)
• Estimated Median of grouped data


  L + ((1/2n - F)/f)W