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

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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

i'll put the answer up in a few days.... i would like other people to have an attempt at the question first.answer is b?

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 step-by-step guide to filling in the sample table and making various calculations of statistical measures. i hope that this lecture, The Sample Table: Walk-Through #1, will make that process a little easier for anyone who needs clarity on the topic.

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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