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Find the Area Under the Standard Normal Curve between Two Z-scores

 

Example: Find the area under the standard normal curve between and .

In the example of the standard normal curve, we will calculate the area between Z=-1.35 and Z=2.01.

 

Method 1:  Normalcdf(lowerbound, upperbound,  ) computes the area between a lowerbound and an upperbound.  In this example, you are computing the area from -1.35 to 2.01.

 

To calculate the area between -1.35 and 2.01, press 2nd [DISTR] and select 2:normalcdf(and type in

-1.35 , 2.01 , 0 , 1 ) and press ENTER.

 

 

Method 2:  This method calculates the area, and also displays a graph of the probability distribution.  Press WINDOW and set Xmin equal to -3 and set Xmax equal to 3.  Set Xscl equal to 1.  Set Ymax = .5  Set Ymin = .5/4.

 

Press 2nd [QUIT] .  Clear all the previous drawings by pressing 2nd [DRAW] and selecting 1:ClrDraw and pressing ENTER ENTER.  Press 2nd [STATPLOT] and TURN OFF all PLOTS.  Now you can draw the probability distribution.  Press 2nd [DISTR].  Highlight DRAW and select 1:ShadeNorm( and type in -1.35 , 2.01 , 0 , 1 ) and press ENTER.  The output displays a normal curve with the appropriate area shaded in and its value computed.