Question 1
Suppose that the following model was fit to a set of data.
E(
y) =
β0 +
β1x1 +
β2x2The corresponding plot if residuals against predicted values
is shown. Interpret the plot.
◦ It appears that the variance of
ε is not constant.
◦ It appears that a quadratic model would be a better fit.
◦ The residuals appear to be randomly scattered so that no model modifications are necessary.
◦ It appears that the data contain an outlier.
Question 2
A public health researcher wants to use regression to predict the sun safety knowledge of pre-school children. The researcher randomly sampled 35 preschoolers, assigned them to one of two groups, and then measured the following three variables:
SUNSCORE:
y = Score on sun-safety comprehension test
READING:
x
1 = Reading comprehension score
GROUP:
x
2 = 1 if child received a Be Sun Safe demonstration, 0 if not
A regression model was fit and the following residual plot was observed.
Which of the following assumptions appears violated based on this plot?
◦ The mean of the errors is zero
◦ The errors are normally distributed
◦ The variance of the errors is constant
◦ The errors are independent
Interventions to promote safety for children
Health Risks Associated with Levels of Body Fat
Regression Analysis
Health care setting.
Food Safety and Technology
Ecological model for environmental health