A widely reported finding that the risk of divorce increases when wives fall ill — but not when men do — is invalid, thanks to a short string of mistaken coding that negates the original conclusions, published in the March issue of the Journal of Health and Social Behavior.
The paper, “In Sickness and in Health? Physical Illness as a Risk Factor for Marital Dissolution in Later Life,” garnered coverage in many news outlets, including The Washington Post, New York magazine’s The Science of Us blog, The Huffington Post, and the UK’s Daily Mail .
But an error in a single line of the coding that analyzed the data means the conclusions in the paper — and all the news stories about those conclusions — are “more nuanced,” according to first author Amelia Karraker, an assistant professor at Iowa State University.
Karraker — who seems to be handling the case quickly and responsibly — emailed us how she realized the error:
Shortly after the paper was published some colleagues from Bowling Green State, I-Fen Lin and Susan Brown, emailed me and my co-author about our estimate of divorce. They were trying to replicate the paper and couldn’t understand why their estimate was so much lower than ours. I sent them the statistical analysis file, which documents all of the steps as to how we came to all the estimates in the paper. And they pointed out to us, to our horror, that we had miscoded the dependent variable…As soon as we realized we made the mistake, we contacted the editor and told him what was happening, and said we made a mistake, we accept responsibility for it.
Speaking to us on the phone, Karraker added:
People who left the study were actually miscoded as getting divorced.
Using the corrected code, Karraker and her co-author did the analysis again, and found the results stand only when wives develop heart problems, not other illnesses. She said:
What we find in the corrected analysis is we still see evidence that when wives become sick marriages are at an elevated risk of divorce, whereas we don’t see any relationship between divorce and husbands’ illness. We see this in a very specific case, which is in the onset of heart problems. So basically its a more nuanced finding. The finding is not quite as strong.
In the original study, Karraker and her co-author relied on data from 2,701 heterosexual marriages that were included in the Health and Retirement Study at the University of Michigan, which follows 20,000 Americans older than 50. They parsed it with computer code, finding out how many marriages seemed to be felled by one of four serious diseases: cancer, heart disease, stroke and lung disease. They found that marriages were 6% more likely to end if the wife falls seriously ill than if she’s healthy, while the same was not true when the husband fell ill.
Having a mistake pointed out is part of the process of doing science, Karraker said:
The original code will be available online. The code that we used for all the estimates. That’s part of good research practice: somebody should be able to replicate your results. We talked with I-fen Lin and Susan Brown, and really appreciated them raising this with us. While you would never want to discover that you made a mistake, what’s ultimately important is to do good research, and sometimes that requires you to make a correction. We’ve tried to be completely transparent about the mistake that we made and correcting it as quickly and clearly as possible.
We spoke to several others involved in the case, who agreed that Karraker took responsibility and handled the error as smoothly as possible.
We are conducting research on gray divorce (couples divorce after age 50) using the Health and Retirement Study, the same data set used in Dr. Karraker’s paper. Her published numbers (32% of the sample got divorced) are very different from our estimates (5%), so we contacted her to clarify the discrepancy.
That’s when they emailed Karraker, who sent them the code later that day. They alerted Karraker to the error, and she got in touch with the the journal’s editor, Gilbert Gee “promptly,” Gee told us.
Karraker and Lantham’s paper had a major error in their statistical code that was discovered by another research team. The authors contacted the journal’s office about this error promptly. The authors then reanalyzed their data and submitted a corrected paper. This paper was reviewed by senior members of our editorial board, met our standards of peer review, and will be republished in the September, 2015, issue of JHSB. Although regrettable, mistakes happen to all researchers. In my opinion, Karraker and Lantham met the highest standards of professionalism in correcting their mistake.
According to Gee, the new version of the paper will include a statement from the editor — which he told us he’d send after a few colleagues reviewed it — along with a memo from the researchers about what happened.
For now, here’s the official retraction note in full:
The authors have retracted the article titled “In Sickness and in Health? Physical Illness as a Risk Factor for Marital Dissolution in Later Life,” published in the Journal of Health and Social Behavior (2015, 56(1):59-73). There was a major error in the coding in their dependent variable of marital status. The conclusions of that paper should be considered invalid. A corrected version of the paper will be published in the September 2015 issue of JHSB.
We asked Karraker’s co-author, Indiana University-Purdue University Indianapolis sociologist Kenzie Latham, for a statement. Her take on things was pretty much the same as Karraker’s:
In general, this is an unfortunate mistake that occurred, and we have taken steps to correct our error in a timely and transparent manner. Prior to submitting our paper to the Journal of Health and Social Behavior, we spent quite a bit of time soliciting feedback. We sent copies of our paper to senior scholars to review and we presented our findings at conferences and workshops. The original manuscript went through multiple rounds of peer-review before being accepted for publication.
We also asked if she had any advice for researchers that find themselves in a similar situation:
Errors will occur when conducting research–even when researchers take steps to minimize these types of errors. The most important piece of advice is to be forthcoming with your mistakes and correct them so that the scientific literature can advance.
Here’s the original coding line:
replace event`i’ = 1 if delta_mct`i’ != 0 | spouse_delta_mct`i’ != 0
And here’s the corrected coding:
replace event`i’ = 1 if (delta_mct`i’ != 0 | spouse_delta_mct`i’ != 0) & delta_mct`i’ != . & spouse_delta_mct`i’ != .
The study has not been cited, according to Thomson Scientific’s Web of Knowledge.
Hat tip: Rolf Degen
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