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Formulas/maths/Statistics

Statistics

Mean of Ungrouped Data
Calculates the arithmetic mean of a set of n observations.
Class Mark of a Class Interval
Gives the midpoint value that represents a continuous class interval.
Mean of Grouped Data (Direct Method)
Computes the arithmetic mean for grouped or frequency distribution data.
Mean by Assumed Mean Method
Calculates the mean using deviations from an assumed mean a to simplify arithmetic.
Mean by Step Deviation Method
Calculates the mean for equal class width h using scaled deviation step values.
Combined Mean of Two Groups
Gives the pooled arithmetic mean of two groups having sizes n₁ and n₂.
Median of Ungrouped Data
Finds the middle observation of an arranged numerical dataset.
Median of Grouped Data
Computes the median from the median class of a continuous frequency distribution.
Mode of Grouped Data
Calculates the mode for continuous grouped data from the modal class.
Empirical Relation Between Mean, Median, Mode
Approximates the relationship between the three central tendencies for moderately skewed distributions.
Range of a Dataset
Measures statistical dispersion as the difference between extreme values.
Mean Deviation About Mean
Calculates the mean absolute deviation of observations from their arithmetic mean.
Mean Deviation About Median
Calculates the mean absolute deviation of observations taken about their median.
Variance of Ungrouped Data
Computes the variance of n individual observations from raw sums of squares and mean.
Standard Deviation
Defines standard deviation as the positive square root of the variance.
Variance of Grouped Data
Calculates the variance of a frequency distribution using frequencies and class marks.
Variance of First n Natural Numbers
Gives the exact variance for the first n consecutive natural numbers 1, 2, ..., n.
Effect of Linear Transformation on Mean
Shows that a change of origin by b and scale by a shifts the mean accordingly.
Effect of Linear Transformation on Variance
Shows that variance is independent of change of origin and scales quadratically.
Combined Variance of Two Groups
Calculates the combined variance of two pooled datasets with different sizes and means.
Coefficient of Variation
Measures relative variability to compare consistency across distributions with positive means.
Minimality of Sum of Squared Deviations
States that the sum of squared deviations is strictly minimised when taken about the mean.