Software developers: Coding interviews are a disaster, and here's why

Standard technical interviews don't measure coding skills properly and only test how nervous candidates get, say researchers.

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The technical interviews often used in hiring software engineers are a failure because they only test whether a candidate has performance anxiety, rather than whether they are good at coding.

The interviews may also be used to exclude groups or favour specific job candidates, a study from North Carolina State University and Microsoft has found.

"Technical interviews are feared and hated in the industry, and it turns out that these interview techniques may also be hurting the industry's ability to find and hire skilled software engineers," said Chris Parnin, an assistant professor of computer science at NC State and co-author of a paper on the work.

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The study suggests that a lot of well-qualified job candidates are being eliminated because they're not used to working on a whiteboard in front of an audience.

Technical interviews for software developers are often based around giving a job candidate a coding problem to solve, then asking the candidate to write out their code on a whiteboard while explaining each step. Many developers have argued that the technical interview process is deeply flawed, so the researchers decided to look at the effect of the interview process on aspiring software engineers.

They conducted technical interviews of 48 computer science undergraduates and graduate students. Half were given a standard technical interview, with an interviewer looking on.

The other half of the participants were asked to solve their problem on a whiteboard in a private room, without the need to explain their code, and with no interviewers watching.

People who were given the traditional interview performed half as well as those who were able to work in private.

"The findings suggest that companies are missing out on really good programmers because those programmers aren't good at writing on a whiteboard and explaining their work out loud while coding," said Parnin.

The researchers also said that standard technical interviews may also be used to exclude certain job candidates -- interviewers could give easier problems to favourite candidates, for example -- or to serve as a barrier to others. The researchers noted that in their study, all of the women who took the public interview failed, while all of the women who took the private interview passed. "The idea that the very design of the interview process may effectively exclude an entire class of job candidates is troubling," the researchers said.

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The nature of the technical interview process also means that many job candidates try to spend weeks or months training specifically for the interview, and not the actual job they would be doing.

"The technical interview process gives people with industry connections an advantage," says Mahnaz Behroozi, first author of the study. "But it gives a particularly large advantage to people who can afford to take the time to focus solely on preparing for an interview process that has very little to do with the nature of the work itself."