The process for creating an interaction term in SUDAAN involves first identifying the two or more variables that will be included in the interaction term. These variables should be categorical or continuous and have a meaningful relationship. Then, the user must specify the type of interaction (e.g. product, sum, difference) and the order of the interaction (e.g. first or second order). The interaction term is then calculated by multiplying or combining the two variables according to the specified type and order. Finally, the interaction term can be included in statistical models and analyses to assess its impact on the outcome variable.
How do I create an interaction term in SUDAAN? | SUDAAN FAQ
In proc regress, proc rlogist and proc survival, you can use
a * between two variables (such as two categorical variables or one categorical and one continuous
variable) to create an interaction term on the model statement. However, you
cannot do this with two continuous variables; you need to create the interaction term in a data
step before running the model. For example, srsex and racehpra
are categorical variables. In the example below, we create the
interaction term between srsex and racehpra.
proc regress data=temp1 filetype=sas design = jackknife; weight rakedw0; jackwgts rakedw1--rakedw80 / adjjack=1; model ab23 = srsex racehpra srsex*racehpra; subgroup srsex racehpra; levels 2 4; run;Number of observations read : 55428 Weighted count: 23847415 Observations used in the analysis : 1000 Weighted count: 466228 Denominator degrees of freedom : 80 Maximum number of estimable parameters for the model is 8 Weighted mean response is 42.854796 Multiple R-Square for the dependent variable AB23: 0.081618 Variance Estimation Method: Replicate Weight Jackknife Working Correlations: Independent Link Function: Identity Response variable AB23: AB23 ---------------------------------------------------------------------- Independent P-value Variables and Beta T-Test Effects Coeff. SE Beta T-Test B=0 B=0 ---------------------------------------------------------------------- Intercept 47.87 1.81 26.51 0.0000 SRSEX MALE 1.63 2.41 0.68 0.5011 FEMALE 0.00 0.00 . . RACEHPRA LATINO -9.67 2.04 -4.75 0.0000 PACIFIC ISLANDER 4.32 6.03 0.72 0.4757 AIAN -3.47 2.68 -1.29 0.1992 ASIAN 0.00 0.00 . . SRSEX, RACEHPRA MALE, LATINO 3.51 3.09 1.14 0.2596 MALE, PACIFIC ISLANDER -5.64 7.27 -0.78 0.4398 MALE, AIAN -0.39 3.49 -0.11 0.9108 MALE, ASIAN 0.00 0.00 . . FEMALE, LATINO 0.00 0.00 . . FEMALE, PACIFIC ISLANDER 0.00 0.00 . . FEMALE, AIAN 0.00 0.00 . . FEMALE, ASIAN 0.00 0.00 . . ---------------------------------------------------------------------- ------------------------------------------------------- Contrast Degrees of P-value Freedom Wald F Wald F ------------------------------------------------------- OVERALL MODEL 8 960.50 0.0000 MODEL MINUS INTERCEPT 7 8.59 0.0000 INTERCEPT . . . SRSEX . . . RACEHPRA . . . SRSEX * RACEHPRA 3 1.12 0.3457 -------------------------------------------------------
In the next example, we will create an interaction term using a categorical
variable, racehpra, and a continuous variable, ae13.
proc regress data=temp1 filetype=sas design = jackknife; weight rakedw0; jackwgts rakedw1--rakedw80 / adjjack=1; model ab23 = ae13 racehpra ae13*racehpra; subgroup racehpra; levels 4; run;Number of observations read : 55428 Weighted count: 23847415 Observations used in the analysis : 322 Weighted count: 158239 Denominator degrees of freedom : 80 Maximum number of estimable parameters for the model is 8 Weighted mean response is 40.890349 Multiple R-Square for the dependent variable AB23: 0.058683 Variance Estimation Method: Replicate Weight Jackknife Working Correlations: Independent Link Function: Identity Response variable AB23: AB23 ---------------------------------------------------------------------- Independent P-value Variables and Beta T-Test Effects Coeff. SE Beta T-Test B=0 B=0 ---------------------------------------------------------------------- Intercept 46.99 3.16 14.87 0.0000 AE13 -0.15 1.13 -0.14 0.8917 RACEHPRA LATINO -5.02 3.64 -1.38 0.1715 PACIFIC ISLANDER -9.37 7.35 -1.28 0.2057 AIAN -4.19 4.37 -0.96 0.3396 ASIAN 0.00 0.00 . . AE13, RACEHPRA 1, LATINO -0.89 1.36 -0.66 0.5113 1, PACIFIC ISLANDER 4.09 1.65 2.49 0.0150 1, AIAN -0.47 1.45 -0.33 0.7435 1, ASIAN 0.00 0.00 . . ---------------------------------------------------------------------- ------------------------------------------------------- Contrast Degrees of P-value Freedom Wald F Wald F ------------------------------------------------------- OVERALL MODEL 8 257.15 0.0000 MODEL MINUS INTERCEPT 7 4.35 0.0004 INTERCEPT . . . AE13 . . . RACEHPRA 3 0.93 0.4289 AE13 * RACEHPRA 3 4.76 0.0042 -------------------------------------------------------
In the example below, we try to use two continuous variables, ae13 and ae14, to create the interaction term. The error message
that was displayed in the log is shown below. If you want to include this
type of interaction term in your model, you will need to create it in a data
step before running the procedure and include it on the model statement.
proc regress data=temp1 filetype=sas design = jackknife; weight rakedw0; jackwgts rakedw1--rakedw80 / adjjack=1; model ab23 = ae13 ae14 ae13*ae14; run;SEMANTIC ERROR : (Message 452) At most one continuous variable is allowed in each term of the RHS of a MODEL statement
Cite this article
stats writer (2024). What is the process for creating an interaction term in SUDAAN?. PSYCHOLOGICAL SCALES. Retrieved from https://scales.arabpsychology.com/stats/what-is-the-process-for-creating-an-interaction-term-in-sudaan/
stats writer. "What is the process for creating an interaction term in SUDAAN?." PSYCHOLOGICAL SCALES, 1 Jul. 2024, https://scales.arabpsychology.com/stats/what-is-the-process-for-creating-an-interaction-term-in-sudaan/.
stats writer. "What is the process for creating an interaction term in SUDAAN?." PSYCHOLOGICAL SCALES, 2024. https://scales.arabpsychology.com/stats/what-is-the-process-for-creating-an-interaction-term-in-sudaan/.
stats writer (2024) 'What is the process for creating an interaction term in SUDAAN?', PSYCHOLOGICAL SCALES. Available at: https://scales.arabpsychology.com/stats/what-is-the-process-for-creating-an-interaction-term-in-sudaan/.
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