Thursday, September 8, 2022

Casio fx-991EX Classwiz Tips: Normal Distribution

Casio fx-991EX Classwiz Tips:  Normal Distribution


This week I am going to show some things that can be done with the Casio fx-991EX Classwiz.  


The Normal Distribution 


The Classwiz's Distribution mode has calculations for the following probability distributions:


1.  Normal, f(x) = exp(-1/2 * ((x - μ) / σ)^2 ) / (σ * √(2 * π))

2.  Binomial

3.  Poisson


This is Mode 7.


Normal CD - Finding the Area


[ MENU ], 7: Distribution, 2: Normal CD


The CDF function calculates the area (probability) between two limits.   The lower and upper tail areas require the limits to be -∞ and +∞, respectively.  However, the Classwiz does not provide values for -∞ and +∞.  For the best estimate, I suggest using -7 and 7 are the limits.  The calculator calculates the probability from -7 to 7 to be 1.


Example:

(For all the examples, the standard values μ = 0, σ = 1)


Lower tail area to x = 3:  lower limit = -7, upper limit = 3; area:  0.9986501019


Lower limit = -2, upper limit = 2; area:  0.954499736


Upper tail from x = -1:  lower limit = 1, upper limit = 7; area:  0.1586552539


Inverse CD


[ MENU ], 7: Distribution, 3: Inverse Normal


This calculation gets the point value for a lower tail distribution (-∞ to x).


Example:

(For all the examples, the standard values μ = 0, σ = 1)


Area = 0.5; xInv:  0


Area = 0.6; xInv: 0.2533470931


Area = 0.7; xInv: 0.5244004382


Eddie


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