Note: Your answers to the questions below should follow the expectations for homework found here. Questions outside of class can be asked on the Module Assignments-Questions Teams channel (see link on homepage).

Nurse Wages

In this previous exercise you prepared the variables required of an IVR. Continue that exercise by answering the questions below. Be careful and specific with your interpretations (i.e., refer to slopes and intercepts and to specific groups in the data (not “reference group” and “first group”)).

  1. Write the ultimate full model for this situation.
  2. Create a table like that in the reading that shows the sub-model for each group.
  3. Interpret the meanings of each parameter in your model.
  4. What type of value (positive, negative, zero) would you expect for β if wage increased with increasing months of experience for both groups? Explain.
  5. What type of value would you expect for γ1 if mean wage increased at a slower rate with increasing months of experience for male than female nurses? Explain.
  6. What type of value would you expect for δ1 if the mean wage for females with no experience was the same as the mean wage for males with no experience? Explain.
  7. What type of value would you expect for δ1 if γ1=0 and the mean wage for females was less than the mean wage for males with the same amount of experience? Explain.

 

Turtle Nesting Ecology

In this previous exercise you prepared the variables required of an IVR. Continue that exercise by answering the questions below. Be careful and specific with your interpretations (i.e., refer to slopes and intercepts and to specific groups in the data (not “reference group” and “first group”)).

  1. Write the ultimate full model for this situation.
  2. Create a table like that in the reading that shows the sub-model for each group.

The data for this situation are in HawksbillTurtles.csv (data, meta). Load these data and reorder the regions so that it will be easier to distinguish regions in the Middle East (Arabian Gulf, Indian Ocean, and Red Sea) from those in the Atlantic (Caribbean and West Atlantic) and allow the Arabian Gulf to be the reference group. [Note: see this for help.] Then fit the ultimate full model and create a table of parameter estimates (and confidence intervals) that can be used to answer the questions below. Be careful and specific with your interpretations (i.e., refer to slopes and intercepts and to specific groups in the data (not “reference group” and “first group”)).

  1. Interpret the meaning of the “(Intercept)” confidence interval.
  2. Interpret the meaning of the confidence interval in the row with your covariate variable.
  3. Interpret the meaning of the confidence interval in the row with your first interaction variable.
  4. Interpret the meaning of the confidence interval in the row with your third indicator variable.
  5. Predict (“by hand” and showing your work) the mean clutch size for all turtles from the “Arabian Gulf”, “Caribbean”, and the “Indian Ocean” with a curved carapace length of 90 cm. [You don’t need a confidence interval for this and don’t use any additional R code.]
  6. Confirm your predictions in the previous question using two lines of R code.

 

Water Quality Near a Gold Mine

In this previous exercise you prepared the variables required of an IVR. Continue that exercise by answering the questions below. Be careful and specific with your interpretations (i.e., refer to slopes and intercepts and to specific groups in the data (not “reference group” and “first group”)).

  1. Write the ultimate full model for this situation.
  2. Create a table like that in the reading that shows the sub-model for each group.

The data for this situation are in GoldMine.csv. Load these data and reorder the groups so that total phosphorous is the reference group … see this for help. Then fit the ultimate full model and create a table of parameter estimates (and confidence intervals) that can be used to answer the questions below. Be careful and specific with your interpretations (i.e., refer to slopes and intercepts and to specific groups in the data (not “reference group” and “first group”)).

  1. Interpret the meaning of the confidence interval in the row with your covariate variable.
  2. Interpret the meaning of the “(Intercept)” confidence interval.
  3. Interpret the meaning of the confidence interval in the row with your first indicator variable.
  4. Interpret the meaning of the confidence interval in the row with your second interaction variable.

Also do the following in R.

  1. Construct a plot that shows the separate regression lines for the groups.