. A study is designed to assess the relativeantiarrhythmic activity of fixed dos
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Question
. A study is designed to assess the relativeantiarrhythmic activity of fixed doses of 2 beta
adrenergic blocking agents, propranolol and acebutolol, in aprospective double-blind crossover trial. Eight patients who had atleast 30 premature ventricular contractions (PVCs) per hour whilereceiving placebo were entered into the study. They receivedpropranolol for 6 weeks, were weaned off this medication, and thenunderwent 6 weeks of using acebutolol. At the end of the first 6weeks the number of PVCs/hour were measured. Then at the end of thestudy this was again measured for each subject. The data istabulated below.
Patient
PVC/hour
Propranolol
Acebutolol
1
82
129
2
87
107
3
103
132
4
79
102
5
76
143
6
96
99
7
88
127
8
104
121
A. Is there a statistically significantdifference in mean PVC/hour between the 2 beta
adrenergic blocking agents? Perform this test at 95% confidence.Use a paired t-test.
B. Explain why a paired t-test is the correcttest to do here.
Patient
PVC/hour
Propranolol
Acebutolol
1
82
129
2
87
107
3
103
132
4
79
102
5
76
143
6
96
99
7
88
127
8
104
121
Explanation / Answer
(A)Paired T-Testand CI: Propranolol, Acebutolol
Paired T forPropranolol - Acebutolol
N Mean StDev SEMean
Propranolol8 89.375 10.636 3.760
Acebutolol 8 120.000 15.757 5.571
Difference 8 -30.6250 19.9423 7.0507
95% CI formean difference: (-47.2972, -13.9528)
T-Test of meandifference = 0 (vs not = 0): T-Value = -4.34 P-Value =0.003
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