Gifted Issues Discussion homepage Forums Identification, Testing & Assessment A score of 160 -- what does it really mean?

When a test mean is 100 and the standard deviation is 15, then a score of 160 should appear in approximately 1 out of 31,560 people. Correct?

A few questions:
1. How is it possible to assess the rarity of scores above, say 145, when the normative samples for these tests are only a few thousand?

2. Why is it that achievement scores of 160 are anecdotally way more common than IQ scores of 160?

3. On achievement tests like the WIAT and WJ, is it possible to interpret a raw score that exceeds the minimum required for a 160? (some kind of 'extended norms'?)

-Ul.H.