C Appendix: Symbols, formulas, statistics and parameters

Symbols used

TABLE C.1: Some symbols used
Symbol Meaning Reference
H0 Null hypothesis Sect. 28.2
H1 Alternative hypothesis Sect. 28.2
df Degrees of freedom Sect. 31.4
CI Confidence interval Chap. 21
s.e. Standard error Def. 18.3
n Sample size
χ2 The chi-squared test statistic Sect. 31.4

Confidence intervals

Almost all confidence intervals have the form

statistic±(multiplier×s.e.(statistic)). Notes:

  • The multiplier is approximately 2 for an approximate 95% CI (based on the 68–95–99.7 rule).
  • multiplier×s.e.(statistic) is called the margin of error.
  • Confidence intervals for odds ratios are slightly different, so this formula does not apply for odds ratios. For the same reason, a standard error for ORs is not given.

Hypothesis testing

For many hypothesis tests, the test statistic is a t-scores, which has the form:

t=statisticparameters.e.(statistic) Notes:

  • Since t-scores are a little like z-scores, the 68–95–99.7 rule can be used to approximate P-values.
  • Tests involving odds ratios do not use t-scores, so this formula does not apply for tests involving odds ratios.
  • For tests involving odds ratios, the test statistic is a χ2 score and not t-score. For the same reason, a standard error for ORs is not given.
  • The χ2 statistic is approximately like a z-score with a value of (where df is the ‘degrees of freedom’ given in the software output):

χ2df.

TABLE C.2: Some sample statistics used to estimate population parameters. Empty table cells means that these are not studied. The asterisk means that no formula is given in this text.
Parameter Statistic Standard error S.E. formula reference
Proportion p ˆp s.e.(ˆp)=ˆp×(1ˆp)n Def. 20.2
Mean μ ˉx s.e.(ˉx)=sn Def. 22.1
Standard deviation σ s
Mean difference μd ˉd s.e.(ˉd)=sdn Def. 23.2
Diff. between mean μ1μ2 ˉx1ˉx2 s.e.(ˉx1ˉx2)
Odds ratio Pop. OR Sample OR s.e.(sample OR)
Correlation ρ r
Slope of regression line β1 b1 s.e.(b1)
Intercept of regression line β0 b0 s.e.(b0)
R-squared R2