BE205-worksheet11 by Tim Downing https://padlet.com/tim_downing1/BE205worksheet11 Add questions or answers here as text or photos or word documents en-us 2016-09-25 13:53:16 UTC 2025-12-10 14:12:41 UTC hello@padlet.com Bayes and odds ratios tim_downing1 https://padlet.com/tim_downing1/BE205worksheet11/wish/139647482 Q1. A patient goes to see a doctor. The doctor performs a test with 99% reliability: 99% of people who are sick test positive and 99% of healthy people test negative. The doctor knows that only 1% of people are sick. If the patient tests positive, what is the chance the patient is really sick?
Q2. If only 90% of healthy people test negative, how does this probability change? Likewise, if the prevalence of the sickness is 10%, how would that change the original posterior probability calculation?
Q3. 90% of Dan's Dodgy tomatoes treated with a pesticide are diseased with Bacillus but only 10% of Simon's Splendiferous tomatoes are diseased. In a group not treated with a pesticide, 55% of Dan's Dodgy tomatoes are diseased and 45% of Simon's Splendiferous tomatoes are. What is the odds ratio of disease rates given pesticide exposure between varieties?
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