Hi,

Important to Understand z -values as they relate to the Standard Normal curve:

Below:  z = 0, z = ± 1, z= ±2 , z= ±3 are plotted.  

Note: z = 0 (x value the mean) 50% of the area under the curve is to the left and %50 to the right



1) mean of 72 and a standard deviation of 4.

*Need to KNOw: 

    z = (X-72)/4 = -2.00 

       X = -8 + 72 = 64   (z-score tells us X is less than the average of 72

2)P(z = -.40) = 34.46%  = invNorm(-.40)

TI syntax is invNorm(area to left of desired z). 

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