SOC SCI 10A Chapter Notes - Chapter 7-8: Normal Distribution, Percentile Rank, Percentile
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Standard normal distribution is also know as z This is also an idealization, a mathematical model designed to describe an ideal version of a shape which many real distributions come close to. Just like there are no perfect circles in the world just things that come close to being perfect. A bell curve is the normal or ideal shape of a graph. There is only one normal shaped distribution for every possible mean and non zero standard deviation. The percentile rank of the z score is a score 0-50% Percentiles of the standard normal distribution may be found by reversing the procedure for nding percentile ranks. To nd the ith percentile in the standard normal distribution. Find the cumulative proportions in the body of the z table that are closest to the cumulative proportion computed in step 1. The ith percentile is the lowest z score with a cumulative proportion as if as the cumulative proportion in step 1.
