Stupid things employers ask candidates at job interviews

Question Mark

Many of the common questions people ask in job interviews aren't actually that helpful in predicting how well a person will do in a job, experts say.

Instead of finding the best job candidates, they end up finding the people who are best at selling themselves in job interviews.

What's your greatest weakness? If you're trying to find the best employees, it could be just asking that question.

"There are some really good people out there who are not glib, and because they're not glib they're not getting the job," said Priscilla Claman, president of Boston-based consulting firm Career Strategies.

(Read more: Think twice about faking your resume )

In general, researchers say the entire job interview process can work against finding the best candidate because it favors people who are sociable, practiced at interviewing and have physical traits such as being tall or having nice teeth.

"What it does is it amplifies all the biases that we have," said Lauren Rivera, an associate professor of management and organizations at Northwestern University's Kellogg School of Management.

Rivera's research has found that employers also tend to hire people they'd like to hang out with.

Of course it's important for employees get along, but Rivera said there's a danger in relying too heavily on that, and not enough on whether the person has the skills to do the job.

(Read more: Economy's sticky problem: Older and jobless )

"There are a lot of well-liked people who aren't particularly competent," she said.

Instead of asking cutesy, hypothetical or casual questions, researchers say employers are better off asking every candidate consistent, concrete questions that are directly related to the job the person is going to be doing.

Jeffrey Daum, CEO emeritus at the consulting firm Competency Management, said he urges employers to base their questions on the qualities they see in the best employees they already have. Those may not be the same skills that make people good job interviews, like being extroverted or extremely well spoken.

"If the person isn't going to be a public speaker as the primary aspect of their job, then their ability to communicate in a flowing manner is far less important than the content of what they're communicating to you," Daum said.

Here are some of the worst offending questions:

What's your greatest weakness?

Questions about a person's greatest strength or weakness don't do much more than tell you how well a person has been trained to answer interview questions, researchers say. Ditto for the old nugget, "Where do you see yourself in five years?"

Rivera's pet peeve: "Tell me about a time that you demonstrated leadership."

"It tests someone's familiarity with the type of stories you're supposed to tell an employer," she said.

How many garbage cans are there in New York City?

Jobseekers have been inundated in recent years with oddball logic questions like, "How many red cars are there in Cleveland?" or "If you were a pizza deliveryman, how would you benefit from scissors?"

These questions are meant to show how a person thinks, but the answers are way too subjective to give you a good idea of how you can do a particular job, Claman said. They also work against people who just don't see the logic in being asked a question that's totally unrelated to their ability to do a job.

"It won't pick the person who says, 'What the hell is this person asking this stupid question for?'" she said.

What three things would you bring to a desert island?

These related oddball questions revolve around theoretical personal choices, such as "What celebrity would you have dinner with?" and "If you were 80 years old, what would you tell your children?"

Experts say that can tell you a lot about what a person is like, and whether you have similar tastes in music or survival gear. But it's not going to give you a good idea of whether the person will show up on time or can write great lines of code.

As the economy slowly improves, researchers say, there's another danger to asking these kinds of cutesy questions instead of practical ones: You'll alienate your best candidates.

That's why Donald Truxillo, a professor of industrial and organizational psychology at Portland State University, dislikes questions like, "How many uses could you have for a spoon?"

"Unless someone has come up with a really good scoring key for that, all it does is make the interviewer feel clever," he said.

Are you planning to have children?

One of the biggest mistakes an interviewer can make is to ask personal questions that are at best inappropriate and at work legally questionable. Pro tip: Don't ask candidates if they are married, have kids or are pregnant, even in casual conversation.

What's your SAT score?

There's been a mini fad lately of asking people who are long out of college to provide such data as SAT scores or college grade point averages.

Experts say there are two problems with this line of questioning: These tests and measures aren't necessarily predictive of your ability to succeed in the working world, and they can be biased toward people from certain socioeconomic backgrounds.

Claman suspects people are asking these questions because they want a piece of hard data to evaluate candidates on. The problem is that it's not a very useful piece of hard data, she said.

Hypothethically speaking ...

Hypothetically speaking, it sounds like a good idea to ask candidates what they would do if they were given a particular task at your company.

In reality, Daum said, it's much more useful to have the job candidate tell you about something they actually did, and to keep drilling down on real examples that show how they work in real-life settings.

(Read more: Stay-at-home dads struggle to shake Mr. Mom image )

You can even have the person show their skills by actually writing a few lines of code or doing another hands-on project.

"A lot of people are good at giving a hypothetical example, but they're not so good at actually doing it on the job," Daum said.

-By CNBC's Allison Linn. Follow her on Twitter @allisondlinn and Google or send her an email .

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