Case Study

Based on the core structure of the multiple regression equation, how should the researcher explain the way these three variables (X1X_1, X2X_2, and X3X_3) will be mathematically combined to predict the outcome (YY)? Justify your explanation using the components of the general formula.

Case context: A clinical psychologist is investigating the factors that contribute to therapy success. They decide to predict a patient's therapy success score (YY) based on three distinct variables: number of therapy sessions (X1X_1), patient motivation (X2X_2), and therapist experience (X3X_3). The researcher plans to use a standard multiple regression analysis to model this relationship.

Question: Based on the core structure of the multiple regression equation, how should the researcher explain the way these three variables (X1X_1, X2X_2, and X3X_3) will be mathematically combined to predict the outcome (YY)? Justify your explanation using the components of the general formula.

Sample answer: The researcher should explain that the predicted therapy success score (YY) will be expressed as an additive combination of the three predictor variables. According to the formula structure, each individual predictor (X1X_1, X2X_2, and X3X_3) will be multiplied by its own corresponding regression weight (b1b_1, b2b_2, and b3b_3). These three weighted terms are then added together (b1X1+b2X2+b3X3b_1X_1 + b_2X_2 + b_3X_3) to estimate the predicted outcome (YY).

Key points:

  • Identifies that the predicted outcome (YY) is an additive combination of variables
  • Explains that each predictor (XX) is paired with a corresponding regression weight (bb)
  • Justifies the combination by demonstrating the summation of the weighted terms (e.g., b1X1+b2X2+b3X3b_1X_1 + b_2X_2 + b_3X_3)

Rubric: The response must explain that the predictors are combined additively, with each predictor being paired with (multiplied by) a corresponding regression weight before being summed to equal the predicted outcome.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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