Radiation Oncology/Medical Statistics/Distribution

Characteristics of Distribution Need to specify if variable is discrete or continuous Location: Mean (μ): average value Median: value that divides the probability distribution in half, meaning half of values are above it and half are below it Mean and median are the same for symmetrical distributions, and different for skewed distribution. Extreme values of X influence mean much more than median Spread: Variance (σ2): the mean value for all variables of the distance from x to mean, squared. Calculated as the mean of (X-μ)2 Standard deviation (σ): square root of the variance. Effectively the mean difference of variable x from mean Mean and standard distribution provide approximate distribution of the variables