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