A community for students.
Here's the question you clicked on:
 0 viewing
jpattisha
 11 months ago
3. A particular diagnostic test for disease X has a sensitivity of 90% and a specificity of 90%. What is the negative predictive value of the test?
jpattisha
 11 months ago
3. A particular diagnostic test for disease X has a sensitivity of 90% and a specificity of 90%. What is the negative predictive value of the test?

This Question is Open

JimQ
 11 months ago
Best ResponseYou've already chosen the best response.0I had to check on this one. It is not possible to get from sensitivity/specificity to PPV/NPV without an estimate of the population prevalence of the disease. It has apparently been suggested that the PPV/NPV values be normalized assuming a 50% prevalence rate. I don't know whether 50% is an acceptable estimate of prevalence for your class. Once you have the prevalence, you should build a table like the one from Wikipedia: http://en.wikipedia.org/wiki/Sensitivity_and_specificity Populate each box with a % as follows: The first box is Positive for Condition and for Disease. Since the test has a sensitivity of 90% and 50% of the population is assumed to have the disease: \[\frac{ TruePositive }{ AllTests }=\frac{ TruePositive }{ AllPositive }*\frac{ AllPositive }{ AllTests }\] \[\frac{ TruePositive }{ AllTests }=Sensitivity*Prevalence(50pct)\] The formula above will work with other values for prevalence. The rest of the algebra is pretty straightforward.
Ask your own question
Sign UpFind more explanations on OpenStudy
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.