I recently spoke to a large group of HR professionals at a meeting of the New Zealand Institute of Human Resources. A wide variety of organizations and experts attended. Add to this a bad case of the flu and it became a challenging direction.

During Question Time, an interesting question sparked a lot of discussion: “When it comes to hiring, how many tests is too many?” I like to use the medical analogy that if you want to control diabetes there is no need to drain all the blood from your body; a complete vile will do.

The same analogy applies to psychometric tests. Some of my contemporaries are putting applicants through 3+ hour assessments or, God forbid, an all day assessment center process. Here, applicants are subjected to many practical work simulation tests, as well as a series of self-report tests.

Two more hours of testing is an exaggeration. Collins (2003) conducted a meta-analysis: a study of 524 individual correlations between measures of personality and cognitive ability and job performance in assessment centers. The result was a whopping 83. Their conclusion: Most of the valid variance in overall test center scores can be captured with good mental (cognitive) ability and personality measures that can be completed in an hour or so! an hour and a half!

The only winners, when it comes to long testing procedures, are the developers of the testing procedure, who in many cases have no training in organizational psychology. These promoters will charge a high fee for many reports that are unlikely to be read by a busy executive, or worse, filled with so many psychos that they won’t understand!

So back to the question, “How much is too much?” This depends on the job title and the expected number of applicants. If there are a large number of applicants and you are recruiting for a mid- to low-level position, you may want to use a quick pre-screening assessment to select those who don’t “fit.”

Here you are looking for a broad overview, for example a look at scores on the Big 5 personality dimensions, plus a short cognitive test that measures verbal and numerical ability, or it could be a quick attitude (integrity) test. . A tool like PeopleCLUES is ideal for this purpose. It is inexpensive and takes about 25 minutes to complete.

On the other hand, if the role is a managerial or professional position and you have a smaller pool of applicants, I would recommend a “deeper” assessment like Rembrandt or ASSESS. I would still like to do this test before the main interview. This allows you to go into the main interview armed with a complete picture of the candidate. You can then use the interview and reference process to validate the information obtained from the profile.

Typically, the length of testing time is governed by the depth of information required, and this depth is correlated with the level of the job. In a nutshell, the tests will revolve around four basic dimensions: personality profiles, mental ability tests, value inventories, and motives (how and why the candidate will do the job).

Do you need to perform all these tests? Well, if you have the budget and time, you’ll certainly cover all the bases and have a complete profile of the candidate’s attributes and skills, but do you need all this information to make an informed decision?

As much as I like to see all this information, I don’t think it adds much to the decision-making process; as psychologists, we refer to this as adding incremental validity. On top of this, do we really need to subject candidates to this intense scrutiny or spend that much money?

This raises the question: “What would serve as the basis for profiling candidates for most jobs?” The research is pretty clear; a combination of two tests will usually give you enough incremental validity to make a safe decision. Let’s review our medical analogy. A vile of blood will highlight a diabetic problem, but hey, while you’re here, let’s have another vile to check your cholesterol levels.

A list of the validity levels of the tests used in the selection process can give you a clearer picture and a useful guide for questioning test developers to justify a variety of tests or expensive assessment center tests:

Personality, Mental Ability, Motives, and Interests (Work-Paired).75 Personality, Mental Ability, and Motives.66 Mental Ability and Integrity.65 Mental Ability and Structured Behavioral Interview.63 Mental Ability and Work Sample Test.60 Test of personality and mental capacity .58 Work sample test.54 Mental ability test.51 Structured behavioral interview.51 Job knowledge test.48 Integrity test.41 Personality test.40 Assessment centers.38 Personal data (information forms application).35 References.26 Years of work experience.18 Unstructured interview.14 Years of education.10 Interests.10 Graphology.02

Note: Mental ability tests may also be called cognitive or intelligence tests;

correlations relate to overall job performance. When tests are validated with a specific job role, correlations can increase. As an example, a recent study we did on Rembrandt personality tests, aligned to a specific sales role, returned a correlation of .70.

In summary, the point I’m trying to make is that psychometric tests, while not a panacea for selecting the right person for the first time, are backed by strong scientific evidence to add incremental power to the selection process. Combine this with a behavior based interview and multiple qualifications and you have at least a 75 to 80% chance of getting it right. Much better odds than most managers now get with their casual glance at a CV, a general chat that doubles as an interview, and a tertiary reference check.