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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