explain why we need to adjust for the number of months of observation when we model the number of utis

INSTRUCTIONS TO CANDIDATES

ANSWER ALL QUESTIONS

Question 1 

van den Broek (1995) describes a study of 98 HIV-infected men attending the Utrecht University Hospital. The research question of interest is whether the number of urinary tract infections (UTIs) experienced in the period of observation, was associated with the patient’s immune status. Immune status is determined by measuring the CD4+ cell count, with high CD4+ indicating high or good immune status, and a low CD4+ count indicating a compromised immune system and progression of HIV. CD4+ is reported as the number of cells per cubic millimetre of blood, with a normal CD4+ count being in the range 500 to 1500. The dataset is available on iLearn as uti.csv.

Variable name Description episode number of UTIs in the period of observation months number of months of observation sqrt_sd4 square-rooted transformed of CD4+ count

You should:

a) explain why we need to adjust for the number of months of observation when we model the number of UTIs. Also explain how we can carry out the adjustment in a count regression setting.

b) investigate the data graphically (including some visualisations to check whether zero-inflated models should be considered).

c)  start by fitting a Poisson model with sqrt_cd4 as your covariate and then try to find the most appropriate distribution for this dataset by consider alternative models. Use an appropriate model selection criterion to assist you.

• Make sure you add in the adjustment from part a). The help menu can be of assistant if you need help.

• You can drop/add sqrt_cd4 as your covariate as part of your model building process. • You can assume any Negative Binomial model to have constant shape.

d) write down the fitted model equation for your final model.

e) obtain the quantile residuals of your final model and check its goodness of fit.

f) interpret your model parameters.

g) summarise your finding in a sentence or two.

Attachments:

Expert's Answer

529 Times Downloaded

Related Questions

. The fundamental operations of create, read, update, and delete (CRUD) in either Python or Java

CS 340 Milestone One Guidelines and Rubric  Overview: For this assignment, you will implement the fundamental operations of create, read, update,

. Develop a program to emulate a purchase transaction at a retail store. This  program will have two classes, a LineItem class and a Transaction class

Retail Transaction Programming Project  Project Requirements:  Develop a program to emulate a purchase transaction at a retail store. This

. The following program contains five errors. Identify the errors and fix them

7COM1028   Secure Systems Programming   Referral Coursework: Secure

. Accepts the following from a user: Item Name Item Quantity Item Price Allows the user to create a file to store the sales receipt contents

Create a GUI program that:Accepts the following from a user:Item NameItem QuantityItem PriceAllows the user to create a file to store the sales receip

. The final project will encompass developing a web service using a software stack and implementing an industry-standard interface. Regardless of whether you choose to pursue application development goals as a pure developer or as a software engineer

CS 340 Final Project Guidelines and Rubric  Overview The final project will encompass developing a web service using a software stack and impleme