That's probably b/c the manufacturer says on their website that the RIAS is a 30-35 minute test: http://www3.parinc.com/products/product.aspx?Productid=RIAS

They list the RIST at taking 10-15 minutes: http://www3.parinc.com/products/product.aspx?Productid=RIST

Maybe they are testing some kids who miss a lot of questions and are done quickly?

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