Question

J Morton et al examined gallbladder function before and after fundoplication - a surgery used to stop stomach contents from flowing back into the esophagus (acid reflux) - in patients with gastroesophageal reflux disease.  The authors measured gallbladder functionality by calculating the gallbladder ejection fraction (GBEF) before and after fundoplication for 12 patients.  The goal of fundoplication is to increase GBEF, which is measured as a percent.  The data are shown below.  Can we conclude that fundoplication increases GBEF functioning?  Construct a 95% confidence interval.

   Preop %     22.0    63.3      96       9.2        3.1      50.0      33        69.0        64         18.8      10           34

   Postop %    65.5    91.5      59     39.8      10.1      19.6      41        89.8        86         55.0      88         40

Answer 1

SOLUTION-

WE USE MINITAB-16 FOR FINDING OUT THE 95% CONFIDENCE INTERVAL

LET BE THE MEAN GBEF BEFORE THE TEST AND BE THE MEAN GBEF AFTER THE TEST.

THE APPROPRIATE HYPOTHESIS FOR THIS SCENARIO WOULD BE,

WE PERFORM A PAIRED-T TEST IN ORDER TO FIND THE 95% CONFIDENCE INTERVAL

STEPS: ENTER THE DATA IN SEPERATE COLUMNS> STAT> BASIC STATISTICS> PAIRED-T> IN FIRST SAMPLE, ENTER THE POST-DATA AND IN SECOND SAMPLE, THE PRE-DATA> UNDER OPTIONS, SET THE CONFIDENCE LEVEL 95.0; THE TEST DIFFERENCE 0 AND THE ALTERNATE AS 'GREATER THAN'> CLICK OK

OBSERVATION- THE VALUE OF TEST STATISTIC IS 1.98 WITH A P-VALUE OF 0.037.

THE 95% LOWER BOUND OBTAINED IS 1.65.

ANSWER- THE 95% LOWER BOUND OBTAINED IS 1.65

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