Hi All,
Just a quick note to clarify what's going with the Stata output for Question 1a on Homework 7. Recall that self-reported smoking status was validated in a subsample of participants:
Urinary Cotinine
| E+ E- |
-----------------+------------------------
Self Report E+ | 402 159 |
E- | 113 1481 |
-----------------+------------------------
To calculate the necessary quantities in Stata, one should submit diagti TP FN FP TN, where TP = true positives (402), FN = false negatives (113), FP = false positives (159), and TN = true negatives (1481) --> diagti 402 113 159 1481.The output includes the following table:
True |
disease | Test result
status | Neg. Pos. | Total
-----------+----------------------+----------
Normal | 1,481 159 | 1,640
Abnormal | 113 402 | 515
-----------+----------------------+----------
Total | 1,594 561 | 2,155
"True disease status" corresponds to Urinary Cotinine, where Normal corresponds to non-smoking (E-) and Abnormal corresponds to smoking (E+). "Test result" corresponds to Self Report, where Neg corresponds to non-smoking and Pos corresponds to smoking. The table is confusing, but comparable to the one offered in the prompt. Stata also calculates the correct sensitivity, specificity, PPV, and NPV.
Good luck on the final!
Best,
Rebecca