Biostatistics

Terms

Sensitivity
Specificity
Positive Predictive value
Negative Predictive value

p-value

• probability of getting the difference at least as big as that observed if the null hypothesis is true

two-sided p-value

• include the possiblity that the difference could have been of the same size but in the opposite direction.

Trials

Pilot

• feasibility of delivering a treatment

Phase I

• toxicity-finding and dose-determination

Phase II

• clinical efficacy, traditional stopping rules for allow for as many as 14 consecutive nonresponders.

Phase III

• Randomized trial.

Tests

Parametric methods: assume normal distribution
non-Parametric methods: uses ranks and particularly useful in small data sets.

Purpose of test	non-parametric Method	Parametric counterpart
Difference between paired observation	Wilcoxon signed rank test (sign test)	Paired t-test
Difference between two groups	Wilcoxon rank sum test	two-sample t-test
Difference between 2 or more groups	Kruskal-Wallis one-way analysis of variance	One-way analysis of variance

Chi-squared test

• test whether there is an association between row variables and column variables
• ie. binary groups and binary outcome.

Fisher exact test

• a form of chi-squared test where chi-squared test is not a good enough approximateion
• ie. overall total of the table is < 20
• or overall total is 20 - 40 and smallest of the four expected number is < 5.

Regression Model

	Regression model
Type of outcome variable	Type	Measure of exposure effect	Effects
Numerical, Continuous	Linear	mean difference	Additive
Numerical, Ordered	Ordinal	mean difference	Additive
Binary	Logistic	Odds ratio	Multiplicative
Matched binary	Conditional logistic	Odds ratio	Multiplicative
Time to binary event	Poisson	Rate ratio	Multiplicative
Time to binary event	Cox	Hazard ratio	Multiplicative

Display Data

Box-and-whisker plot

• displaying a distribution of data.

Life Tables

• display survival patterns of successive time points.

Kaplan-meier Estimate

• is life table with continuous time line.