More hiring mistakes are made in the first 30 minutes of a job interview than at any other time. This is devastating if you’re a candidate who should have been hired. It’s equally devastating if you’re the hiring manger and hire the wrong person. I contend that these errors are the primary reason 70% of the U.S. workforce is disengaged. The solution is simple:

Don’t use the interview to make the hiring decision. Use the interview to collect the evidence needed to make the hiring decision.

Of course, if you don’t know what evidence to look for, this simple solution is a bit more challenging. To address this I suggest preparing a performance-based job description before the interview. A performance-based job description lists the top 6-8 things a person in the job needs to accomplish in order to be considered successful. For example, for a sales position one objective could be, “Open 3-4 new accounts per month by identifying and personally meeting with the key decision makers at each account.” This is a lot better than saying the person must have 5+ years of sales experience selling to the same types of customers in the same industry.

Determining the candidate’s ability and motivation to do the actual work required is the purpose of the interview. However, if the interviewer doesn’t know what’s actually required, the person is left to his or her own devices to determine this. Given this loosey-goosey condition, most interviewers determine if the candidate is hirable in the first 5-10 minutes of the interview based on affability, appearance and communication skills. Once this preliminary yes/no hiring decision is made, the balance of the interview is used to gather confirming evidence to validate the decision. It’s easy to see how the lack of job knowledge combined with unscientific and biased interviewing techniques can result in bad hiring decisions.

Given this state of affairs here’s a simple technique to convert the interview into an evidence-gathering process:

  • Get every interviewer on the same page by sharing the performance-based job description ahead of time. Here’s a completed profile for a product manager. You can see how using this can instantly change the focus of the entire interviewing process.
  • Do not give anyone a full yes/no hiring decision. Instead, assign each interviewer a narrower responsibility to evaluate the candidate’s ability to achieve just one or two of the performance objectives listed.
  • Have each interviewer ask the one-question Performance-based Interview for each of the performance objectives assigned. This question provides all of the evidence needed to determine competency and motivation.
  • Eliminate gladiator voting (up vs. down) to make the final hiring decision. Instead have each interviewer share his or her evidence using this type of Quality of Hire Talent Scorecard ranking system. Redo the interview if any rankings vary too much. This indicates a process that’s out of control.

Of course, first impressions and related biases will still get in the way. To short-circuit this I suggest interviewers recognize their initial positive or negative reaction to the candidate and then take some type of offsetting action. One way to do this is to be more cynical with those whom you like and more open-minded with those you don’t.

If you’re the candidate being improperly assessed, it’s unlikely the interviewer has read this posting and followed the techniques described. In this case you’ll need to take matters into your own hands. Here’s how to shift the odds back into your favor:

  • If you feel the interviewer is purposely seeking negative information, you’ll need to intervene right away. One way to do this is to ask the interviewer how the trait, factor or skill being asked about is actually used on the job. Then give an example of something you’ve accomplished that relates to this requirement.
  • To prevent the interviewer’s personal biases from kicking in too soon, ask the person to describe some of the big challenges involved with the open job at the beginning of the interview.
  • You can force questions to be asked around your strengths by simply asking, “Is (major strength) an important aspect of this job?” Then give an example of something you’ve accomplished that best demonstrates your ability.
  • Send the interviewer this introduction to the Performance-based Interview before your interview. Of course practice and record your answers. If they’re really good you might even want to send the interviewer your recording. This actually might get you the interview, too.

Bottom line: Don’t use the interview to make the hiring decision. Use the interview to collect the evidence needed to make the hiring decision. This simple change in perspective changes everything. More important, it will eliminate 50% of all hiring mistakes you’re ever likely to make.