HCAD 5220
Fall 2015
Ed Schumacher
Homework 4
(Due September 22)
1. Suppose we are provided with the following information concerning the time required to
perform two different services:
Service A: Sample size=12, 𝑥̅ = 14.5, s=3.90
Service B: Sample size=12, 𝑥̅ = 22.0, s=5.39
a. Test at the level of significance =.05 whether it is reasonable to assume that the
two samples came from populations having the same variance.
b. Using the p-value, test at the level of significance =.05 whether the mean time
required for service B is greater than for service A. Be sure to provide an
interpretation of the p-value.
2. At BigCounty Community Hospital the administrator has implemented multiple
innovations to attempt to reduce overall length of stay in the hospital. You have been
asked to assess if these efforts have been successful. The Excel file titled Homework
4.xlsx, the work sheet “Big_Hospital_Data.xlsx” contains data on a sample of patients for
2012 and 2014.
a) What is the overall average LOS in 2012 and in 2014? Is there evidence for
decreased LOS?
b) Is there evidence that LOS decreased within DRG?
3. One of the more frustrating problems plaguing hospitals and laboratories is the rate with
which bacteria external to the patient contaminate blood cultures. Blood culture
contaminations extend hospital stays and increase the cost of care. One of the keys to
preventing infections is using proper specimen collection technique. Profiteering
Community Hospital (PCH) is worried about their contamination rate and has taken steps
to try to reduce it. They established a program to more fully standardize the collection
process to ensure that all collections were done using the same technique. They are now
interested to know if this program has reduced the infection rate. PCH collected data on
blood samples taken in their hospital over two periods. Those in Period 1 were
specimens collected prior to implementation and those in Period 2 were collected post
implementation. These data are shown in the “Profiteering” worksheet in the Homework
4.xslx file. The file contains the following variables
 Period – 1=pre, 2=post
 Unit – which floor the specimen was collected (a, b, c, d, or ed, where ed is the
emergency department and a, b, c, and d are other units.)
 Collected by – the type of clinician collecting the blood (Patient Care Partner,
RN-Emergency, RN-Inpatient, other)
 Contaminated – yes or no
a) Calculate the number of hours it takes to complete each collection. Is there
evidence that registered nurses are faster than the other groups at collecting the
specimens?
b) What is the average infection rate in the pre-program period and in the after
program period? Is there evidence that the hospital successfully reduced their
infection rate?
c) For those observations in Period 2, is there evidence of a difference in the
infection rate for those collections starting before 6:00pm and those starting after
6pm?
d) Are nurses significantly better at collecting specimen than the other groups?
e) Is there a relationship between contaminations and the type of clinician collecting
the specimen?