Notation and symbols

∑	Greek letter sigma, denoting sum of. ∑x is shorthand for $$ \sum_{i=1}^{n}{x_i} $$
\| x \|	absolute value of x
α	probability of a Type I error; or level of hypothesis test, usually 0.05
β	probability of a Type II error
χ²	value from the Chi-squared distribution, see Chi-squared table
CI	confidence interval
CR	coefficient of repeatability
DF	degrees of freedom
F	value from the F-distribution, see F-Distribution critical values table
K	kappa
n or N	sample size
P	probability of hypothesis
r	Pearson correlation coefficient
r_s	Spearman rank correlation coefficient
R²	coefficient of determination
RSD	relative standard deviation
s	standard deviation
s²	variance
SD	standard deviation
SEM	standard error of the mean
t	value from the t-distribution, see t-distribution table
z	value from the Normal distribution, see Normal distribution table