Scores on the Stanford-Binet Intelligence scale have a mean of 100 and a standard deviation of 16, and are presumed to be normally distributed. A person who scores 68 on this scale has what percentile rank within the population?

Question

Scores on the Stanford-Binet Intelligence scale have a mean of 100 and a standard deviation of 16, and are presumed to be normally distributed.  A person who scores 68 on this scale has what percentile rank within the population?

z = (68-100)/16
z = -32/16 = -2
So would it be 95% or 62%??

PsyDAG · Answer

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to that Z score. Remember that it is below the mean, and percentile rank is % ≤ that score.