Prcheat

[ganges]

I desperately need this program for probability, seeing that school isnt about to start for another 5 days i wont be able to do anything wihtout this.

Could any1 please send me this program or where i can find it on the net?

[Collin Li]

I recommend these default calculator functions as a substitute, found under [2nd] [DISTR] (the VARS button):

normalcdf() = ,
where X is a normally distributed random variable with mean and standard deviation
(Hint: Use "1e99" and "-1e99" for infinity and negative infinity, respectively)

For a binomial distribution, X, with trials and a probability of success :

binompdf(n,p,x) = ,

binomcdf(n,p,x) =

Once you learn how to use these, you will never go back. These functions are so much more versatile than PRCHEAT.

Here are some reasons why:

1. You can then use Ans, after using these functions - something you can't do with PRCHEAT.

2. PRCHEAT cannot solve problems where is unknown, for example. The calculator can do this if you are clever with the functions.

[ausyid]

Never used PrCheat, and never needed to, thanks to the calculator functions coblin has mentioned.

Just a quick question coblin - is there a possibility that they could ask you to find n on the exams for something that isn't Pr(X > or = 1), or ie 1 - Pr(X=0). Because I know you can work those out on the calculator, I just don't know how?

[Collin Li]

Yeah, you should be able to work out those problems for on the calculator for any value of .

For inequalities, you will have to make use of the binomcdf( function.

Let's say we want to find the least number of required such that

Since ,

Plot Y1 = 1 - binomcdf(X,p,49)     (X being the calculator's variable, not the random variable X)

Use TABLE, and scroll down until you find the first value of (X) which gives a Y1 > 0.99

(Hint: make sure your table settings are set at so that the increments are integer steps -- the only possible values of . Also, you should tweak your starting position on the table, to avoid having to scroll down for 20+ rows in some cases)

[ausyid]

Ahh thankyou.

I actually had been taught that, I had just forgotten it.

Really love probability, whilst I do not like the rest of the methods course.

[sxcalexc]

I was just wondering... the assessors don't actually require you write binomcdf(....), for example, do they? As long as you have say Pr(X > x) = 0.15 and Pr(Z > z) = 0.15. The actual 'z' value can just be found straight on the calculator right?

[Collin Li]

I'd probably write it as just for my own convenience, because that's what the calculator responds to.