hypothesis testing fundamentals

© 2012 by HealthCare Quality Improvement Solutions, LLC

HealthCare Quality Improvement Solutions


• What is hypothesis testing?

A quantitative method for answering questions and determining whether potential factors significantly effect process performance

2


• Primary purpose from a quality improvement perspective:

Determine whether the outcome of interest is produced by a similar or dissimilar process

3


75%

72%

77%

95%

71%

60%

Physician Similar Processes

Discharge Rx ACEI 75%

Hospital Performance

P-Value 0.567 P-Value 0.001

Dissimilar Processes



4

Potential Factors


Similar Processes

• Critical few factors will not be identified

• Redesign the process


• Critical few factors will be identified

• Focus quality improvement on the critical few factors

5


• 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

6


• 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

7


• The null hypothesis H0:

Asserts there is no difference among factors

• The alternate hypothesis HA:

Asserts that there is a difference among factors

8


• The legal process is not perfect

Innocent defendants can be found guilty by the jury

In hypothesis testing this is known as a Type I Error

– Rejecting the null hypothesis when it is true

Guilty defendants can be found innocent by the jury

In hypothesis testing this is known as a Type II Error

– Accepting the null hypothesis when it is false

Innocent Guilty

Innocent Correct Incorrect

Guilty Incorrect Correct

Truth

Jury Decision

Legal Process

H0 True H0 False

Accept H0 Correct Type II Error -

Reject H0 Type I Error -

Correct

Actual State

Decision

Data Analysis

9


• 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

10


• 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


• Level of Significance ( ) – also referred to as alpha

0.05

11

© 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?

• Hypotheses: H0: Weekday Median = Weekend Median


• Level of Significance 0.05

P-Value

Yes


• Investigate why it takes longer on the weekend to deliver the initial antibiotic.

13

P-Value


• 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

14

• QI Perspective:

The sample measurements are likely being generated by dissimilar processes

The factor is a critical factor effecting performance


75%

72%

77%

95%

71%

60%

Physician Similar Processes



P-Value 0.567 P-Value 0.001




15

Potential Factors


HealthCare Quality Improvement Solutions

Robert Sutter Contact Information

Website: https://sites.google.com/site/robertsutterrnmbamha/

https://sites.google.com/site/robertsutterrnmbamha/

hypothesis testing fundamentals

Documents