Phi coefficient.π Population proportion.
p Sample proportion.
p Probability of obtaining a particular value for a test statistic. If we state that p≤0.05 this
implies that the probability of obtaining such a test statistic value by chance alone is
less than or equal to 1 in 20.
Q Cochran Q statistic.
Q 1 Lower quartile or 25th percentile in a distribution.
Q 2 Median, second quartile, or 50th percentile in a distribution.
Q 3 Upper quartile or 75th percentile in a distribution.
ρ Rho, general notation for a population correlation.
ρs Spearman’s population rank order correlation.
r Pearson (sample) correlation.
rs Spearman’s (sample) rank order correlation.
rtt Reliability of a test.
R Multiple correlation, the correlation between an observed and predicted value.
R^2 Coefficient of determination in a univariate regression model (sometimes called ‘R
squared’). It is an index of the relationship between the explanatory and response
variable and is interpreted as the proportion of variance in the response variable
explained by the linear regression. In a multiple regression R^2 is called the squared
multiple correlation.
σ Population standard deviation.
σ^2 Population variance.
σp Standard error of a population proportion.
S Sample standard deviation (sometimes SD is used).
SS Sum of squares.
S^2 Sample variance.
S^2 p Pooled variance (estimate for t-test).
Sp Pooled standard deviation.
SR Wilcoxon M-W test statistic.
t Test statistic in the t-test.
T Wilcoxon signed ranks test statistic.
U One-sample runs test statistic.
V Cramer’s V statistic.
X A continuous random variable.
X The count value of a binomial variable.
‘x-bar’ a sample average.
Xi Individual value for the random variable X.
z Fisher’s z transformation value.
Z Z deviate from the normal distribution or Z score.