Applied Biostatistics for the Health Sciences. Richard J. Rossi

Applied Biostatistics for the Health Sciences - Richard J. Rossi


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associated with the drug/treatment, its benefits, and its optimal use. The primary aim of a phase IV trial is to evaluate the long-term safety and effectiveness of a drug/treatment. Phase IV trials sometimes result in a drug being taken completely off the market or new restrictions being placed on the use of the drug. Phase IV trials are also referred to as expanded safety trials and usually involve a very large number of subjects.

      Note that the number of subjects in a trial usually increases as the phases of the study progress. That is, a phase I trial usually involves fewer subjects than a phase II trial, a phase II trial usually involves fewer subjects than a phase III trial, and a phase III trial usually involves fewer subjects than a phase IV trial. Also, some research studies involving human subjects will have less than four phases. For example, it is not unusual for screening, prevention, diagnostic, genetic, and quality-of-life studies to be conducted in only phase I or II trials. However, new drugs and biomedical procedures almost always require phase I, II, and III clinical trials for approval and a phase IV trial to track the safety of the drug after its approval. The development of a new drug may take many years to proceed through the first three phases of the approval process, and following approval, the phase IV trial usually extends over a period of many years.

      Throughout this book several data sets will be used in the examples and exercises. These data sets are available at www.mtech.edu/math/faculty/rick-rossi/Book-Rossi.html as Excel files and MINITAB worksheets; web addresses frequently change at Montana Tech, searching for Rick Rossi on the Montana Tech web page will also allow you to find the data sets on my personal web page.

      Permission to use the Birth Weight, Intensive Care Unit, Coronary Heart Disease, UMASS Aids Research Unit, and Prostate Cancer data sets has been granted by John Wiley & Sons, Inc. These data sets were first published in Applied Logistic Regression (Hosmer, 2000). Permission to use the Body Fat data set has been provided by Roger W. Johnson, Department of Mathematics & Computer Science, South Dakota School of Mines & Technology and the Journal of Statistics Education.

      1.4.1 Birth Weight Data Set

Variable Description Codes/Values Name
1 Identification code ID number ID
2 Low birth weight 1 = BWT≤2500 g LOW
0 = BWT>2500 g
3 Age of mother Years AGE
4 Weight of mother at Pounds LWT
last menstrual period
5 Race 1 = White RACE
2 = Black
3 = Other
6 Smoking status during pregnancy 0 = No SMOKE
1 = Yes
7 History of premature labor 0 = None PTL
1 = One
2 = Two, etc.
8 History of hypertension 0 = No HT
1 = Yes
9 Presence of uterine irritability 0 = No UI
1 = Yes
10 Number of physician visits 0 = None FTV
during the first trimester 1 = One
2 = Two, etc.
11 Birth weight Grams BWT

      1.4.2 Body Fat Data Set