We're unable to sign you in at this time. Please try again in a few minutes.
We were able to sign you in, but your subscription(s) could not be found. Please try again in a few minutes.
There may be a problem with your account. Please contact the AMA Service Center to resolve this issue.
Contact the AMA Service Center:
Telephone: 1 (800) 262-2350 or 1 (312) 670-7827  *   Email: subscriptions@jamanetwork.com
Error Message ......
Comment & Response |

Very Small P Values

Thomas R. Knapp, EdD1; Matthew J. Hayat, PhD2
[+] Author Affiliations
1University of Rochester, Rochester, New York
2Georgia State University, Atlanta
JAMA Psychiatry. 2014;71(8):968-969. doi:10.1001/jamapsychiatry.2014.546.
Text Size: A A A
Published online


To the Editor We are deeply concerned about the article by Hartz et al1 published in JAMA Psychiatry. Most of our concerns have to do with the extremely small P values reported in the text proper and in the tables. Several of them appeared to be beyond the precision capability of the statistical software (SAS) that was used. For example, in their Table 3, an odds ratio of 3.96 (95% CI, 3.61-4.35) is said to have an associated P value of 1.2 × 10−188. The other 4 P values in that table were even smaller. Whether or not those P values have been correctly calculated, there is no reason for reporting anything other than P < .0001, which is the default of SAS for very small P values. (The authors also vacillated between P being equal or less than a certain value.) Furthermore, there is no need for both confidence intervals and P values. If an odds ratio of 1 is not inside the confidence interval, the obtained odds ratio is statistically significant. The odds ratio is the measure of the effect size; the P value is not. And the former takes precedence over the latter.


Sign in

Purchase Options

• Buy this article
• Subscribe to the journal
• Rent this article ?

First Page Preview

View Large
First page PDF preview





August 1, 2014
Sarah M. Hartz, MD, PhD; Laura J. Bierut, MD; Michele T. Pato, MD
1Department of Psychiatry, Washington University in St Louis, St Louis, Missouri
2University of Southern California, Los Angeles
JAMA Psychiatry. 2014;71(8):969. doi:10.1001/jamapsychiatry.2014.707.
Also Meets CME requirements for:
Browse CME for all U.S. States
Accreditation Information
The American Medical Association is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. The AMA designates this journal-based CME activity for a maximum of 1 AMA PRA Category 1 CreditTM per course. Physicians should claim only the credit commensurate with the extent of their participation in the activity. Physicians who complete the CME course and score at least 80% correct on the quiz are eligible for AMA PRA Category 1 CreditTM.
Note: You must get at least of the answers correct to pass this quiz.
Please click the checkbox indicating that you have read the full article in order to submit your answers.
Your answers have been saved for later.
You have not filled in all the answers to complete this quiz
The following questions were not answered:
Sorry, you have unsuccessfully completed this CME quiz with a score of
The following questions were not answered correctly:
Commitment to Change (optional):
Indicate what change(s) you will implement in your practice, if any, based on this CME course.
Your quiz results:
The filled radio buttons indicate your responses. The preferred responses are highlighted
For CME Course: A Proposed Model for Initial Assessment and Management of Acute Heart Failure Syndromes
Indicate what changes(s) you will implement in your practice, if any, based on this CME course.


Some tools below are only available to our subscribers or users with an online account.

0 Citations

Sign in

Purchase Options

• Buy this article
• Subscribe to the journal
• Rent this article ?

Related Content

Customize your page view by dragging & repositioning the boxes below.

See Also...