Statistical Symbols and Abbreviations
Symbol or abbreviation Explanation
α Probability of a type I error, or rejection
level which is typically 0.05
β Probability of Type II error, which is
typically 0.20 (= 1 – power)
µ Mean or average value
σ Standard deviation (for a population)
σ2 Variance (for a population)
var(x) Variance of variable, x
χ2 Chi-square, fitting
Σ Sum of the data
Φ (or ϕ) Phi coefficient, which is the correlation
between 2 by 2 matrix elements
ANOVA Analysis of variance
CI Confidence interval, an estimated range of
values which is likely to include an
unknown population parameter
df Degrees of freedom
F Variance ratio (F distribution), the
distribution of the ratio of two independent
estimates of variance
HO Null hypothesis, assuming no significance
with the hypothesis
HA Alternative hypothesis
N Sample size, the number of whole
population
n The number in a subset
NS Not significant
OR Odds ratio, the odds that an outcome will
occur provided a particular exposure,
compared with the odds of the outcome
occurring without the exposure
P Probability
r (for a sample)
ρ (for a population) Pearson correlation coefficient (-1 to +1),
also called Pearson product moment
correlation
RR Relative risk
rs Spearman’s rank correlation coefficient
R Multiple correlation
