Irfan Ahmed, PhD

Vectors and loops are two tools drawn from computer programming that can be very useful when manipulating data. Their primary use is to perform a large number of similar computations using a relatively small program. Some of the more complicated types of data manipulation can only reasonably be done using vectors and loops. A vector is a set of variables that are linked together because they represent similar things. The purpose of the vector is to provide a single name that can be used to access any of the entire set of variables. A loop is used to tell the computer to perform a set of procedures a specified number of times. Often times we need to perform the same transformation on a large number of variables. By using a loop, we only need to define the transformation once, and can then tell the computer to do the same thing to all the variables using a loop. If you have computer-programming experience then you have likely come across these ideas before. However, what SPSS calls...

Sometimes you may want to explain variability in a continuous DV using several different continuous IVs. Multiple regression allows us to build an equation predicting the value of the DV from the values of two or more IVs. The parameters of this equation can be used to relate the variability in our DV to the variability in specific IVs. Sometimes people use the term multivariate regression to refer to multiple regression, but most statisticians do not use .multiple" and .multivariate" as synonyms. Instead, they use the term .multiple" to describe analyses that examine the effect of two or more IVs on a single DV, while they reserve the term .multivariate" to describe analyses that examine the effect of any number of IVs on two or more DVs. The general form of the multiple regression model is Y i = β 0 + β 1 X i1 + β 2 X i2 + . + β k X ik + å i,. The elements in this equation are the same as those found in simple linear regression, except that we now have k differe...