Key Terms
Notation
X ~ N(mu, sigma)
What it tells you
How many standard deviations x is above or below the mean.
Reverse formula (find x from z)
X = mu + (z)(sigma)
Interpretation
X = 17 is 2 standard deviations to the right of the mean.
Calculator
InvNorm(area to the left, mean, standard deviation)
Process
Multiply sigma by 1, 2, or 3; subtract and add to mu.
Always
Left area + right area = 1.
Example
Middle 50% (IQR): Q1 = invNorm(0.25, mean, SD) Q3 = invNorm(0.75, mean, SD) IQR = Q3 - Q1
Convert
Area to left = 1 - right-tail area, then use invNorm with the left area.