PSY201H1 Chapter Notes - Chapter 5: Percentile Rank, Standard Deviation, Standard Score
18 Oct 2012
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A bell-shaped curve that is described by this equation: Y= frequency of the given value of x* At the bell curve, there are 2 inflection points where the curves go from being convex downward to convex upward, and are at 1 standard deviation from the mean ( +1 and -1 ) Theoretically, it never reaches the horizontal axis, and therefore is asymptotic to it. The area between the inflection points accounts for 50% of the area. Between the mean and 1 standard deviation point = 34. 13% Between the 1st and 2nd standard deviation points = 13. 59. To make a raw score meaningful, you need to find the percentile rank. Remember, the percentile rank is the percentage of scores that are below the given score) If the score is above the , then add 50% to account for the half of the scores below the mean, and find the percentage between the mean and the standard deviation.
