19 For each question below provide a brief 12 sentences resp

19. For each question below, provide a brief (12 sentences) response. a) How is the slope coefficient (b1) in a simple linear regression different from the coefficient (b1) in a multiple linear regression model? b) When would a survival analysis model be used instead of a logistic regression model? c) What is the appropriate statistical test to assess whether there is an association between obesity status (normal weight, overweight, obese) and 5-year incident cardiovascular disease (CVD)? Suppose each participant’s obesity status (category) is known, as is whether they develop CVD over the next 5 years or not.

Solution

a)

A regression coefficient in multiple regression is the slope of the linear relationship between the criterion variable and the part of a predictor variable that is independent of all other predictor variables. In other words it is the rate of change of dependent variable assuming other variables to be constant. While in simple linear regression slope (b1) is simply rate of change of dependent varable with respect to independent variable.

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b)

A survival analysis is used in cases when there are censored observations i.e. when all the events have not been observed.

To accommodate for staggered entry of patients - Usually not all patients are enrolled into the study at the same time. When patients enter at different times during the study and some have not experienced the event at the time of analysis. 3 To utilize detail survival time information. Survival analysis methods are more powerful than logistic regression in general

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c)

A Chi-Square test can be used in order to test the significance of relationship between the two variables if the frequencies are known.