![]() ![]() The reason why will become apparent shortly. We’re going to truncate a random number that lies between 0 and 2. This is a placeholder for the value that’ll be truncated. You’ll have noticed there’s a question mark immediately following the Trunc function in the Numeric Expression box (see above). ![]() Truncate Random Numbers between Zero and Two For example, 2.91 will become 2 and 3.33 will become 3.Īs before, you’ve got to get this function up into the Numeric Expression box, which you can do by dragging and dropping. Or, to put this another way, it truncates a decimal so you’re left with just the integer part of the number. This function has the effect of rounding any decimal number down towards zero. Once you’ve named your target variable, select Arithmetic in the Function group on the left, and then scroll down until you get to the Trunc(1) function. The Truncate FunctionĪs before, the first thing to do is to name our target variable. This time we’re going to combine two functions together to allocate people to a treatment and control condition (where control means getting the placebo). How do you go about it using SPSS?įire up the Compute Variable dialog box again (Transform -> Compute Variable). You want to allocate these people to treatment and control conditions on a random basis. You’ve recruited thirty people for a medical study. Assign People to Treatment and Control Conditions Using Random NumbersĬonsider the following scenario. This means it’s very unlikely you’ll get a duplicate number. One thing to note here is that although you’re seeing only 2 decimal places, SPSS has actually calculated the numbers with much more precision (which you’ll see if you select an individual cell). Just hit OK to generate the variable containing the set of random numbers (in this case between 0 and 100).Īs you can see below, SPSS has created a new variable called RandomNumbers, and filled it with random numbers, each with a value between 0 and 100. ![]() We’ve chosen 0 as our minimum and 100 as our maximum (as above). Just replace each question mark with a value. This signals that you need to specify minimum and maximum values for your random numbers. Specify a Min and MaxĪfter you drag the RV.Uniform function into the Numeric Expression box, you’ll notice it has two question marks after it (see above). You can drag and drop (as above) or use the up arrow in the middle of the dialog. It’s necessary to get the Rv.Uniform function into the Numeric Expression box at the top of the dialog box. Or, to put it a different way, it will generate a random number between two limits, where every possible value between the limits is equally likely to be generated. This returns a random value from a uniform distribution with a specified minimum and maximum value. The function we need is called Rv.Uniform. This will bring up a set of functions, all of which operate to generate different kinds of random numbers. Once you’ve named your target variable, select Random Numbers in the Function group on the right. This is the variable that SPSS will create to hold the set of random numbers. You need to do a number of things to set up this dialog box so SPSS will generate random numbers.įirst, name your target variable. To generate a set of random numbers, we’re going to use SPSS’s Compute Variable dialog box. The ID variable functions to identify the number of cases in a data set for which SPSS will generate random numbers. This tutorial will show you how to generate random numbers in SPSS and also outline a couple of use cases for such a procedure.Īs a starting point, you should at least have an ID variable populated in the Data View of SPSS. ![]()
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