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Thread: Linear regression alayses with interaction effect of two categorical variables

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    Linear regression alayses with interaction effect of two categorical variables




    Dear all,

    I have to run a linear regression analysis in SPSS with an interaction effect of two categorical variables:

    - Modality (audio, visual and audio-visual)
    - Repetition (1x, 2x and 4x)

    I have already dummify the variables. Before I can run the analysis I have to compute the interaction term. But I don't know how I have to do this in the case of a variables with 3 categories (Because I have two dummy variables for each independent variable). Does someone know the formula that I have to enter?

    I hope that someone can help me, thank you in advance !

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    Re: Linear regression alayses with interaction effect of two categorical variables

    This seems like an SPSS issue. In most programs you can just enter a multiplicative term into the model (modality*repetition).
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    Re: Linear regression alayses with interaction effect of two categorical variables

    Thanks a lot ! I have two independent variables that have three categories (so two dummy variables for modality and also two for repetition):

    Modality_Dummy1
    Modality_Dummy 2
    Repetition_Dummy1
    Repetition_Dummy2

    I don't know how I have to enter the multiplicative term. Do you think that I have to include more interaction terms?

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    Re: Linear regression alayses with interaction effect of two categorical variables


    Thanks a lot ! I have two independent variables that have three categories (so two dummy variables for modality and also two for repetition):

    Modality_Dummy1
    Modality_Dummy 2
    Repetition_Dummy1
    Repetition_Dummy2

    I don't know how I have to enter the multiplicative term. Do you think that I have to include more interaction terms?

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