Interviews are an imperfect way to recruit new staff members at the best of times. But while interviews are not perfect, they remain one of the best ways to assess candidates for just about any job.

But interviews are only effective if you ask the right questions – and then make the right assessment of your candidates.

Ask the wrong questions and it’s likely you’ll end up with the wrong candidate in the role, which – according to some evidence – could cost your organisation up to $50,000 in lost productivity and rehiring costs.

Hiring the wrong person for a role can also affect a whole team or even your entire organisation by spreading toxicity to other staff, lowering morale or upsetting clients.

So while you may already have an established, tried and tested interview process for your team or organisation, consider the evidence below and steer clear of these five types of questions in your future interviews:

1. Unstructured Questions

For example: What’s your greatest strength/weakness?

Questions like “What’s your greatest strength?” or “What’s your greatest weakness?” have been a staple of job interviews pretty much since they were invented (apparently that was in 1921, in case you were wondering).

Google’s former head of HR Laszlo Bock calls these sorts of questions “worthless”.

In a widely-referenced research paper, US Professors Frank Schmidt and John Hunter analysed an enormous 85 years of research to identify the most effective methods for hiring people who will excel in their roles – and the least effective.

They found that unstructured interview questions were not a good predictor of success in a role, with a predictive validity of just 38%. (That is, a candidate’s performance in an unstructured interview matches up to how well they go on to perform in their role in just 38% of cases.)

Instead, try using structured interview questions, which are twice as successful at predicting a candidate’s potential work performance.

2. Questions with an obvious answer

For example: How do you think you’d do managing a team for the first time?

It can be really comforting for an interviewer to ask questions like this – you get to hear a candidate say the things you want to hear.

For example, if you’re looking to hire a new manager, it’s comforting to hear someone talk about how much they love managing people, and what a good job they’d do. The better they are at convincing you, the more likely they are to get the job.

Sadly, being convincing doesn’t often correlate to the candidate being good at the job once they’re in it – which is a good reason to avoid questions like this, where the “right” answer is obvious.

Instead, if you want to know how someone would perform at a task, give them a real-life problem and ask them how they would approach it. In the example above, you might ask a new manager:

How would you approach a conversation with a staff member who’s not performing at their job?

Make it a role-play for extra insight – then compare their response to how your other interviewees respond to the same scenario.

3. Sell-yourself questions:

For example: How would your colleagues describe you in 3 words? Or: Why should we give you this job?

If being a good salesperson is at the core of the job then asking a candidate to sell themselves might be worthwhile. For every other role, it’s a waste of time.

Just because a candidate can tell you what they know you want to hear (that they’re smart, experienced, compassionate, resilient etc) doesn’t in any way demonstrate that they are actually any of these things.

If you want to know what someone’s colleagues think of them, the best thing to do is to ask their colleagues directly, via a well-structured reference check.

4. Memory tests

For example: Do you know what our six organisational values are?

Some people have a great ability to memorise things, others not so much. It’s rare that having a great memory correlates to performing well in a job, especially in the age of the internet when it’s simple to look almost anything up on your phone in seconds.

So the usefulness of expecting a candidate to know any particular bit of data or knowledge in an interview is low.

If you’re keen to test someone’s knowledge of a subject area, consider setting them a practical task or a sample work test, and then comparing how each candidate performs in the task.

In Frank Schmidt and John Hunter’s research, sample work tests were the most effective of all forms of assessment at predicting a candidate’s performance in a job.

5. Brain teasers or puzzles

For example: How many ping pong balls would fit in a 747?

Tech companies like Microsoft and Google popularised these sorts of questions in the 1990s as a way to assess software developers’ problem solving skills. More recently, they have stopped using them, with Google’s head of HR noting that:

We found that brainteasers are a complete waste of time. How many golf balls can you fit into an airplane? How many gas stations in Manhattan? A complete waste of time. They don’t predict anything. They serve primarily to make the interviewer feel smart.

The one time you might want to ask a question like this would be if the role itself involves estimation. In that case, it’s better to ask a real-world question that’s as close as possible to a problem the candidate would need to solve in the actual role.

For example, if you’re interviewing a potential fundraiser who would need to regularly estimate a budget for fundraising activities, then give them a realistic scenario and ask them to create a draft budget.

————

Recruiting passionate, dedicated, skilled staff and volunteers is probably the most important thing your organisation can to meet your goals, and doing so will contribute more than almost anything else to increasing your organisation’s impact.

So why take a risk with your recruitment by asking ineffective or just plain useless questions?