Biostatistics
A study was conducted in an area hospital to compare a new method of patient treatment during cardiac surgery with the current standard treatment. The new method of treatment, called FAST-tracking, was designed to speed patient recovery after surgery; one goal of the study was earlier discharge from the hospital. Fast-tracking made several modifications in patient care; among these was the use of steroids for fast-tracked patients.
Investigators were interested in whether there is a meaningful difference in the length of stay (LOS) for patients treated by the FAST-track method, compared to standard care.
The investigators also have a few other concerns about the data. While randomization of patients to one of the two treatment groups can guard against investigator bias in treatment assignment, it does not guarantee balance across all patient characteristics that may impact study outcomes, especially in a small study. Some of these characteristics can have real impact on the outcome of interest.
Older patients tend to have more complications with surgery, and consequently longer hospital stays. The investigators wish to know if there is a difference in age between the patients treated by fast-track and by standard care, since this could affect the hospital length of stay. In addition, women who have cardiac surgery tend to be sicker and have more complications than men having surgery. So there is concern that the treatment groups are balanced for both age and sex.
Another concern is potential side-effects of the new treatment. Since weight gain is a common side-effect of steroid treatment, investigators wish to know if there is a difference in weight gain between the two groups.
A subset of the data recorded for the first 50 patients included in the study at one of the study sites is given below. Data available include:
Subject ID (CASEID) - unique study patient identifier
Treatment group FAST: 1=fast-track, 0=standard care
SEX: 0=male, 1=female
AGE in years
length of stay (LOS) in days
pre-operative weight (PREWT) in pounds
post-operative weight (POSTWT) in pounds.
The data are available in the file fasttrk.MTW or fasttrk.jmp, in Minitab and JMP worksheet format. Note that missing data for a few subjects are indicated by an asterisk (*) in Minitab, or by a dot (. ) in JMP. Data are also available in MS Excel format (fasttrk.xls) for easy import into other stat packages.
Write a brief report that does the following:
- Present descriptive statistics on the study variables of interest
- Address the research questions with presentation of your analysis and results. Your hypotheses, assumptions, results and conclusions should all be clearly stated in your report.
Research Questions:
1. Is there a difference in mean age between patients on the fast-track protocol, and those receiving standard care?
2. Is the proportion of patients who are female in the fast-track group significantly different from the proportion female in the standard care group?
3. Is there a difference in weight gain between patients on the fast-track protocol and those receiving standard care?
4. Is the variability of length of stay similar among patients on the fast-track protocol, and those receiving standard care?
5. Is there a difference in hospital length of stay among patients on the fast-track protocol, and those receiving standard care?
Raw (unedited) computer output is not acceptable as a report. While it is welcome and appropriate to include computer output, any computer output you incorporate directly into the report should be edited for readability (i.e., meaning of codes) and significant digits.
Do not include data presentations in the report that you don't discuss. Include graphics that help illustrate the differences (or lack thereof) that you find. Your report should be no more than 6 pages in length, inclusive of figures and tables.