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