Suppose your friend’s 8th grade sibling is 59.5 inches tall. Their class average height is 63.4 inches with a standard deviation of 2.1 inches. How does this compare to you if you were 70inches?

Answer 1

You can find the percentiles for both your friend and your heights using the z-statistic

z = (x - mean)/std dev, where x = height

For x = 59.5

z = (59.5 - 63.4)/2.1 = -1.86

From standard normal probability table that z value corresponds to 0.0314 or 3.14 percentile.

For x = 70

z = (70 - 63.4)/2.1 = 3.14 which corresponds to 0.9992 or 99.92 percentile.