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Practice questions related to multiple linear regression models and choosing the appropriate statistical test for different scenarios. It covers topics such as the use of linear regression models, adjusted and unadjusted regression coefficients, dummy variables, and interaction terms. It also provides a list of scenarios and asks the reader to choose the most appropriate statistical test for each. useful for students studying statistics or data analysis.
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C797 Practice Questions
c. represent ordinal variables in regression models. d. represent nominal variables in regression models.
1. Consider the following multiple linear regression equation: Y = 2.75 + 13.42 X 1 + .75 X 2 − 4.21 X 3 + 10.30 X 4 Find the predicted value of the dependent variable (ˆY) given the following situations: a. The values of all the independent variables are equal to 0. b. X 1 = 2; X 2 = 3; X 3 = 1; X 4 = − c. X 1 = −1; X 2 = 3; X 3 = −1; X 4 = 8 2. Is BMI associated with eating out in restaurants frequently (more than five times per week on average) after adjusting for gender, age, and race/ethnicity? Use the SPSS data set we used for our example on cholesterol to answer the following questions: o a. First look at a histogram for BMI and decide if you need to log transform the outcome to make it more normal. o b. Next run the linear regression model (make sure to use dummy variables for the race/ethnicity categories) and interpret the results. o c. What is the predicted ln(BMI) of a white woman age 25 who does not eat out often? o d. Is there interaction between gender and eating out often in predicting BMI? ANSWERS
1 (c), 2 (b), 3 (a), 4 (d), 5 (b), 6 (d), 7 (d), 8 (b), 9 (d), 10 (b)
1 (e), 2 (g), 3 (a or g), 4 (e), 5 (b), 6 (g or k), 7 (g),
8 (c), 9 (j), 10 (l)
a. 2. b. −3. c. 78.
a. BMI is somewhat right skewed. After taking the natural log, it seems more normal, so we will use the log-transformed BMI as the outcome in the linear regression model. b. The model explains 9.0% of the variance of BMI and this is statistically significant ( p = .000). Eating out in restaurants frequently is not significantly associated with BMI ( p = .512). However, gender, age, and black race (compared to white) are all significantly positively associated with BMI. c. Predicted ln(BMI) = 3.136 − .015(0) + .016(1) + .003(25)