1. HealthCare Quality
Improvement Solutions
© 2012 by HealthCare Quality Improvement Solutions, LLC

2. • What is hypothesis testing?
 A quantitative method for answering questions and
determining whether potential factors significantly effect
process performance
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© 2012 by HealthCare Quality Improvement Solutions, LLC

3. • Primary purpose from a quality improvement
perspective:
 Determine whether the outcome of interest is produced
by a similar or dissimilar process
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© 2012 by HealthCare Quality Improvement Solutions, LLC

4. Hospital Hospital
Potential Performance Performance
Factors Discharge Discharge
Rx ACEI 75% Rx ACEI 75%
Physician Similar Processes Dissimilar Processes
72% 95%
75% 71%
77% 60%
P-Value 0.567 P-Value 0.001
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© 2012 by HealthCare Quality Improvement Solutions, LLC

5. Similar Processes Dissimilar Processes
• Critical few factors will • Critical few factors will
not be identified be identified
• Redesign the process • Focus quality
improvement on the
critical few factors
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© 2012 by HealthCare Quality Improvement Solutions, LLC

6. • Question to be answered:
 Is the defendant innocent or guilty?
• The defendant is presumed
innocent until proven guilty
 In hypothesis testing this is known
as the null hypothesis and is
denoted H0
 H0: Defendant is innocent
• The plaintiff asserts that the
defendant is guilty
 In hypothesis testing this is known
as the alternate hypothesis and is
denoted HA
 HA: Defendant is guilty
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© 2012 by HealthCare Quality Improvement Solutions, LLC

7. • Potential factor:
 Arrival day of week
• Question:
 Is there a significant difference in Pneumonia Antibiotic
Timing (Median) between patients that arrive on a
Weekday vs. Weekend?
• Hypotheses:
 H0: Weekday Median = Weekend Median
 The antibiotic administration process is similar for weekdays
and weekend
– Arrival day of week does not significantly effect Pneumonia
Antibiotic Timing
 HA: Weekday Median Weekend Median
 The antibiotic administration process is dissimilar for weekdays
and weekend
– Arrival day of week does significantly effect Pneumonia
Antibiotic Timing and is among the Critical Few Factors
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© 2012 by HealthCare Quality Improvement Solutions, LLC

8. • The null hypothesis H0:
 Asserts there is no difference among factors
• The alternate hypothesis HA:
 Asserts that there is a difference among factors
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9. Legal Process
• The legal process is not
perfect Truth
Innocent Guilty
 Innocent defendants can be
found guilty by the jury Jury
Innocent Correct Incorrect
 In hypothesis testing this is Decision Guilty Incorrect Correct
known as a Type I Error
– Rejecting the null
Data Analysis
hypothesis when it is true
 Guilty defendants can be Actual State
found innocent by the jury H0 True H0 False
 In hypothesis testing this is Accept H0 Correct Type II
known as a Type II Error Error -
Decision
– Accepting the null Reject H0 Type I Correct
hypothesis when it is false Error -
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10. • The P-Value is the chance of making a Type I
Error if H0 is rejected
• Decision Criteria:
 If the P-Value is less than or equal to - reject H0
 If the P-Value is greater than - accept H0
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© 2012 by HealthCare Quality Improvement Solutions, LLC

11. • Let’s return to the Pneumonia Antibiotic Timing
question:
 Is there a significant difference in Pneumonia Antibiotic
Timing (Median) between patients that arrive on a
Weekday vs. Weekend?
• Hypotheses:
 H0: Weekday Median = Weekend Median
 HA: Weekday Median Weekend Median
• Level of Significance ( ) – also referred to as
alpha
 0.05
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© 2012 by HealthCare Quality Improvement Solutions, LLC

12. • Let’s return to the Pneumonia Antibiotic Timing
question:
 Is there a significant difference in Pneumonia Antibiotic
Timing (Median) between patients that arrive on a
Weekday vs. Weekend? Yes
• Hypotheses:
 H0: Weekday Median = Weekend Median
 HA: Weekday Median Weekend Median
• Level of Significance
 0.05
P-Value
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© 2012 by HealthCare Quality Improvement Solutions, LLC

13. P-Value
• Investigate why it takes longer on the weekend
to deliver the initial antibiotic.
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14. • When H0 is rejected, the hypothesis test is
considered statistically significant at the selected
level
• It indicates that the sample measurement is
unlikely if the null hypothesis is true
• QI Perspective:
 The sample measurements are likely being
generated by dissimilar processes
 The factor is a critical factor effecting
performance
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© 2012 by HealthCare Quality Improvement Solutions, LLC

15. Hospital Hospital
Potential Performance Performance
Factors Discharge Discharge
Rx ACEI 75% Rx ACEI 75%
Physician Similar Processes Dissimilar Processes
72% 95%
75% 71%
77% 60%
P-Value 0.567 P-Value 0.001
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© 2012 by HealthCare Quality Improvement Solutions, LLC

16. HealthCare Quality
Improvement Solutions
Robert Sutter Contact Information
Website: https://sites.google.com/site/robertsutterrnmbamha/
© 2012 by HealthCare Quality Improvement Solutions, LLC