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#1




Biostats: Question and Answer
An imaginary study is conducted to assess the performance of the antiendomysial antibody test in diagnosing celiac disease. There were 800 people involved in the study and the prevalence of disease was 20%. The study found that the sensitivity and specificity of the test were 75% and 87.5%, respectively. Which of the follow statements is correct?
A) The positive predictive value is 80%. B) The positive likelihood ratio is 6.0. C) The false negative rate 12.5%. D) The negative predictive value is 12.5%. Answer 
#2




biostatic
answer is b?

#3




i'll put the answer up in a few days.... i would like other people to have an attempt at the question first.
i posted the youtube lecture after being alerted to the fact that one obstacle for solving biostats questions is figuring out what the values are for A, B, C, D, etc,. so its not just an explanation to the question (which is not the purpose of the lecture), but a stepbystep guide to filling in the sample table and making various calculations of statistical measures. i hope that this lecture, The Sample Table: WalkThrough #1, will make that process a little easier for anyone who needs clarity on the topic. 
#4




Here's a two by two sample table completely filled in...
This is how the data was calculated based on the information provided... A + C: The number of people with disease is 800 x 20% > 160 B + D: The number of people without disease is 800  160 > 640 A: The number of true positives [(A+C) x sensitivity] is 160 x 75% > 120 C: The number of false negatives [(A+C)  true positives] is 160  120 > 40 D: The number of true negatives [(B+D) x specificity] is 640 * 87.5% > 560 B: The number of false positives [(B+D)  true negatives] is 640  560 > 80 A + B: The total number of positive tests is 120 + 80 > 200 C + D: The total number of negative tests is 40 + 560 > 600
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#5




Answer
Here is the answer to the question...
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