Probability

[David McFarlane]

Marcel,

>I am a new user of e-prime and want to program a card game which has
>the following features:
>
>On each trial 2 cards will be presented, one after another. Before the
>cards are shown participants have to decide whether the number of the
>2nd card will be higher or lower than that of the first card. Now,
>with each card number (numbers 1-5) there is a different probability
>of whether the 2nd card will be higher or lower. For example, for
>number "1" the 2nd card will be higher in 100% of the cases

If the 2nd card must be either higher or lower, then if the first 
card is "1" then the 2nd card *must* be higher with probability 100%, 
you have no choice there.  Same with "5", all other cards are 
lower.  Unless the second card is allowed to be either higher, lower, 
*or the same*, in which case you can bring probability back in.

>, for number "2" the 2nd card will be higher for 75% of the cases 
>and lower for 25% of the cases and so on.

>I have been thinking to do it with an If/then statement. However, I 
>don't know how to program probability in E-prime (I couldn't find it 
>in the help function). Do you know how to do this?

Go to the E-Basic online help (from E-Studio, do Help > E-Basic 
Help), and look at the following topics:

Rnd (function)
Randon (function)
PRNG Object

BTW, an alternate strategy would be to make a list for the first 
cards, and for each first card have a nested list with the allowed 
2nd cards, using list weights to stack the deck for each list of 2nd 
cards.  You cannot tune the probabilies quite so easily this way, but 
it might work well enough.

-- David McFarlane, Professional Faultfinder


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