stars-jpgI’m not a follower of zodiac star signs or related beliefs. Let me just say that right off the bat. I am also not in the business of judging or criticising those who follow the practice.

Having said that, I have read some of my horoscopes in the past that were fairly accurate. After spending some time studying psychology and related disciplines I came to realise that horoscopes and the reading of the stars suffer from one of three psychological effects. It either suffers from the Barnum effect where vague positive generalisations are offered to an individual as specific scientific feedback or the second is something we call confirmation bias where an individual interprets information in a way that confirms that person’s preconceptions. The third trap of astrology is that of the self-fulfilling prophecy which is a case where a prediction [such as a horoscope] directly or indirectly causes itself to become true.

So it piqued my interest when a friend sent me a link to the Good Housekeeping magazine‘s article on star signs that changed. The article states that “NASA has decided to update the astrological signs for the first time in 2,000 years, meaning that a whopping 86% of us now have a different sign.” Including me, I used to be a Taurus, now I’m an Aries, by the thinnest of margins. My birthday is on the 9th of May and Taurus now starts on the 13th.

If you’re still reading, you are probably wondering why I am blogging about star signs and self-fulfilling prophecies. Well I have recently had to make a few presentations to clients to discuss (and in some cases defend) the value of psychometric tests. Psychometric tests have been scientifically researched and it has been proven to be an accurate tool to add to your battery of instruments when making selection decisions.

In 1998, Schmidt and Hunter conducted the largest meta-analysis of personnel selection tools and processes. The abstract from their article reads as follows:

This article summarizes the practical and theoretical implications of 85 years of research in personnel selection. On the basis of meta-analytic findings, this article presents the validity of 19 selection procedures for predicting job performance and training performance and the validity of paired combinations of general mental ability (GMA) and 18 other selection procedures. Overall, the 3 combinations with the highest multivariate validity and utility for job performance were GMA plus a work sample test (mean validity of .63), GMA plus an integrity test (mean validity of .65), and GMA plus a structured interview (mean validity of .63). A further advantage of the latter 2 combinations is that they can be used for both entry level selection and selection of experienced employees. The practical utility implications of these summary findings are substantial. The implications of these research findings for the development of theories of job performance are discussed.

I have referred to this study several times when making a case for the use of psychometrics in selection and development. So back to the topic of this blog post, what has your star sign got to do with it. Thankfully nothing! The table below summarises the use and the effectiveness of different types of selection methods that are used by companies to make selection decisions. On the left hand side the table lists the correlations with future job success with 1.0 being perfect correlation. On the right hand side it shows the frequency which organisations use different kinds of selection tools.

schmidt-and-hunter-table

At the very bottom of this table you can see on the impact of using astrology in selection decisions on the left hand side with a 0.0 correlation. On the right hand side of the table at the bottom you can see that mercifully, nobody uses astrology to predict future job success either.

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