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Testing – The Three A’s – Ability

August 12, 2009

An ability test is also called an IQ (Intelligence Quotient) test – even though the score from an intelligence test is no longer expressed as an actual quotient.  Ability scores are typically a measure of rank on a Gaussian Bell Curve with 100 being average.  That is why school, district and/or state guidelines will define “giftedness” or “service models” based on on a deviation above the mean.  e.g. in Ohio one of the measurements for gifted identification:  the student must “score two standard deviations above the mean minus the standard error of measurement on an intelligence test,”


If x= the average (mean) IQ of 100
1S represents one standard deviation from the mean, and
2S represents two standard deviations from the mean.  


Typically only 2 percent of the population has an ability score above 130. The percentage of the population with ability scores above 145 is less than 1/10 of 1 %. An ability score of 115-129 is between one and two standard deviations above the mean. An ability score of 130-144 is between two and three standard deviations above the mean. An ability score of 145 and above is three or more standard deviations above the mean.

{note: the curve is an approximation and doesn’t fit the upper ends of IQ as predicted. Terman (the inventor of the Standford-Binet) found many more students on the upper end than expected.}

There are many different tests for ability including:  Woodcock Johnson Cognitive Ability Scale, Stanford-Binet Intelligence Scale, Weschler – administered individually and group administered tests like the Otis Lennon, Slosson and Cognitive Abilities Test.  Individual tests are the most accurate and most descriptive and are often required for acceleration consideration.

Ability scores are reliably constant for an individual – although some point variations can occur depending on the test used and the student’s tolerance for testing on that particular day.  Group testing can introduce a number of different variables – someone tapping their foot or coughing or other distraction can negatively impact scores – so testing more than once in a group test environment would be helpful if a private test can not be arranged.  In Ohio, schools are required to offer gifted screening testing regularly and any parent, teacher, friend and even the student themselves, can request one. If your child is “on the bubble” for your school’s service model you should consider retesting as a valid option.

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