Understanding The Relationship Between Marijuana Initiation

## Question

Marijuana initiation | Psychosis | |
---|---|---|

Yes | No | |

Yes | 1222 | 1287 |

No | 703 | 1813 |

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– Which of the following study designs was likely used to gather this information?

Case control

Cohort study

Randomized control Trial

Cross sectional- What measure of association is most appropriate to calculate given the information provided?

Odds Ratio

Risk Ratio

Prevalence Ratio

Rate Ratio

– What type of misclassification has occurred?

Non-differential misclassification of disease

Differential misclassification of exposure

Differential misclassification of disease

Non-differential misclassification of exposure

– Used the information above, calculate the corrected values for the 2X2 table (round to the nearest number) along with the corrected measure of association (round to 2 decimal places)Understanding The Relationship Between Marijuana Initiation .

Marijuana initiation | Psychosis | |
---|---|---|

Yes | No | |

Yes | ||

No |

Measure of Association =

– You stratify your data by gender because you think it might be an important covariable. Using the tables below calculate the stratified measure of association (round to 2 decimal places).

Table A: Females

Marijuana initiation | Psychosis | |
---|---|---|

Yes | No | |

Yes | 308 | 319 |

No | 223 | 406 |

Measure of Association =

Table B: Males

Marijuana initiation | Psychosis | |
---|---|---|

Yes | No | |

Yes | 925 | 957 |

No | 669 | 1218 |

Measure of Association =

– Is the crude association between marijuana initiation and early onset psychosis for the whole sample (the first table) descriptive of the associtation when you look at it broken down by gender (the last two tables)?

No

Yes

2) You are conducting a study looking at the relationship between the presence of a genetic marker and schizophrenia. Here is a 2×2 contingency table indicating if someone has a genetic marker and the presence (or absence) of schizophrenia. Below are the results of your study.

Genetic Marker |
Schizophrenia | |
---|---|---|

Yes | No | |

Yes | 30 | 23 |

No | 39 | 62 |

– Calculate the odds ratio for Schizophrenia for those with the genetic marker compared to those without the genetic marker (round to 2 decimal places).

odds ratio=

– After you finish your study, you realize that some of your research assistants were using an old (and inaccurate) tool for assessment of the genetic marker. This means that among both groups (with and without schizophrenia), 15% of the people you listed as having the genetic marker actually didn’t and 15% of those you listed as not having the genetic marker actually did have the genetic marker.

differential misclassification of disease

non-differential misclassification of exposure

non-differential misclassification of disease

differential misclassification of exposure

– Using the previous misclassification, calculate the new odds ratio (round to 2 decimal places). When calculating the number of people in each cell of your new 2X2 round to the nearest whole number

## Expert Answer

### Step-by-step

**No**