# Epidemiology

rename
drnieves's
version from
2017-06-20 02:27

## Section

Question | Answer |
---|---|

Correct result | There is an effect when one exists. |

Correct result | Null hypothesis rejected |

Correct result | There is no effect when none exists |

Correct result | Null hypothesis accepted. |

Type 1 error | Alternative hypothesis accepted when null hypothesis is correct |

Type 1 error | False positive |

Type 2 error | Null rejected accepted when is false |

Statistical power | 1-B |

Statistical power | Probability of rejecting the null hypothesis when it is false. |

Increase power (decrease B) | Increase sample size, expected effect size, precision of measurement. |

NPV | Proportion of negative test result that are true negative |

Probability that a person actually is disease free given a negative result. | NPV |

NPV | Inversely proportion to pretest probability or prevalence. |

PPV | Proportion of positive test results that are true positive. |

Probability that a person actually has the disease given a positive test. | PPV |

PPV | Directly proportional to pretest probability or prevalence |

Fixed properties of a test | Specificity and sensitivity |

high sensitivity test | Screening in diseases with low prevalence. |

High specificity test | For confirmation after a positive test result. |

Results bias` | Confounding and lead time bias |

Confounding bias | When a factor is related to exposure and outcome, but not on a casual pathway. The factor distorts effect of exposure on outcome. |

Reduce confounding | Multiple/repeated studies |

Cross-over studies | To reduce confounding bias |

Reduce confounding | Matching (pts with similar characteristics in both groups) |

Performing study bias | Recall, measurement, procedure, observer-expectancy bias |

Recall bias | Awareness of disorder alters recall of subjects |

In retrospective studies | Recall bias |

How to reduce recall bias | Reduce time from exposure to follow up |

Measurement bias | Getting information in a way that distorts it |

Reduce measurement bias | Use standardised method for data collection |

Procedure bias | Groups are not treated in the same way |

How to reduce procedure bias | Same as observer-expectancy |

Observer-expectancy bias | Pygmalion effect |

Researcher's belief is tx changes the outcome | Observer-expectancy |

How to reduce observers expectancy bias | Blinding and placebo (lack of awareness) |

Recruiting bias | Selection bias |

Selection bias | Sampling bias. Unrepresentative sample |

Berkson bias | Hospital population vs general |

Healthy worker effect | Healthier than general |

Non response bias | Subjects differ from nonrespondents in meaningful ways. |

How to avoid selection bias | Randomization |

Latent period | Exposure to a risk factor sometimes occurs years before clinical manifestations of a disease are present. |

Lead time bias | When a test dx disease at an earlier time than another test, but does't impact the natural course of the disease. |

Hawthorne | Study subjects change behaviour due to awareness. |

ANOVA (analysis of variance) | to determine whether there are any differences between the means of 2 or more independent groups. |

Null hypothesis rejected when there are at least 2 means that are significantly different from one another | ANOVA |

Meta-analysis | pooling of data from several studies to perform an analysis with greater statistical power than individual studies alone. |

Case fatality rate | number of fatal cases/ total people with condition. |

Question | Answer |
---|---|

Normal distribution | 68- 95-99.7 |

RRR (relative risk reduction) | absolute risk control-absolute risk tx/ absolute risk control |

## Recent badges

## Pages linking here (main versions and versions by same user)

No other pages link to this page. See Linking Quickstart for more info.