The Language of Inferential Statistics
A unique language is used by statisticians to communicate statistical data. A
variety of terms and statistical symbols (Table 13-11) is associated with infer-
ential statistics. Statistical tests are frequently named after the individuals who
devised them, which can sometimes make the names seem arbitrary and hard
to remember. The following fundamental terms are ones with which nurses
should become familiar.
Parametric tests are used to make inferences about the population when
specific conditions have been met (Hayes, 1994; Plichta & Kelvin, 2013). These
conditions include: (1) use of probability sampling, (2) normal distribution of
data, (3) measurement of variables at the interval or ratio level, and (4) reduc-
tion of error. For example, data collected using a visual analog scale would be
analyzed using parametric tests. These important conditions make parametric
tests especially powerful. When parametric tests are used, nurses can have high
levels of confidence about the conclusions made.Symbol/Abbreviation Definition
ANOVA Analysis of variance
df Degrees of freedom
F Fisher’s F ratio
ns Nonsignificant
p Probability
r Pearson product–moment correlation
R Multiple correlation
R^2 Multiple correlation squared
t Computed value of t test
α Alpha; probability of type I error
β Beta; probability of type II error
∆ Delta; amount of change
∑ Sigma; sum or summation
X^2 Chi squareTABLE 13-11
Statistical Symbols for Inferential
StatisticsKEY TERM
parametric:
Inferential statistical
tests involving
interval- or ratio-
level data to make
inferences about
the population362 CHAPTER 13 What Do the Quantitative Data Mean?