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    1: \label{Numerical_Response_Randomization}
    2: 
    3: For LON-CAPA, one of the most important functions is the \texttt{random}
    4: function. Random takes three parameters: a \emph{lower limit}, an \emph{upper
    5: limit}, and an \emph{interval}. The \texttt{\&random} function returns a
    6: random value between the upper and lower limit, some integer number of \emph{interval}'s
    7: away from the lower limit. Thus, for example, \texttt{\&random(1,2,.2)} might
    8: return 1, 1.2, 1.4, 1.6, 1.8, or 2. \texttt{\&random} uses a uniform distribution.
    9: Other distributions are available in LON-CAPA, and can be found by consulting
   10: the function list.
   11: 
   12: %
   13: \begin{figure}
   14: \begin{verbatim}
   15: $a = &random(1.0,10.0,1.0);
   16: 
   17: $b = &random(-10.0,-3.0,1.0);
   18: 
   19: $answer = $a+$b;
   20: \end{verbatim}
   21: 
   22: \caption{Sample \texttt{Random} Calls \label{Sample Random Calls figure}}
   23: \end{figure}
   24: If you put the script in ``Sample Random Calls'' into the
   25: \textbf{Script} block (replacing whatever contents might be in the block
   26: already), you'll get two random variables \$a and \$b. Now, in the \textbf{Text
   27: Block}, put {}``What is \$a plus \$b?'', and in the \textbf{Answer} put
   28: {}``\$answer'', without the quotes for either of them. (It is a good idea
   29: to create a variable to hold the answer and call it \$answer, or some other
   30: reasonably standard name. Do not try to compute the answer in the \textbf{Answer}
   31: field itself; it will not work as you expect.) Now save the problem and \textbf{View}
   32: it. You'll see a randomized problem.
   33: 
   34: For each student, the same random number will be used each time they visit
   35: the problem, but each student will get different random numbers. For any
   36: but the simplest random problems, you'll want to see several random problems
   37: to make sure everything is working out correctly. This is what the \textbf{Random
   38: Seed\index{Random Seed}} field is for. To see another randomized version
   39: of the problem you've just created, put another number into the \textbf{Random
   40: Seed} field and hit \textbf{Change}. It doesn't really matter what number
   41: you put into the field. But for any given \textbf{Random Seed} with the same
   42: problem, you'll see the same randomized problem generated for you. (If you
   43: change the \textbf{Script}, you are no longer guaranteed to get the same
   44: problem.)