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. page revision: 15, last edited: 30 Jun 2007 20:32