Assume that the population distributions of times (in hours) of two different surgeries are normal with equal variances. Two random samples, drawn independently from the populations, showed the following statistics. 
= 10, 
= 2.5, 
= 0.04 
= 11, 
= 2.6, 
= 0.09
Construct and interpret a 90% confidence interval for the true difference in mean amount of time of the two surgeries.
Definitions:
Balloon Angioplasty
A medical procedure that uses a balloon-tipped catheter to widen narrowed or blocked arteries, typically to treat cardiovascular disease.
Blocked Blood Vessels
Obstructions within the arteries or veins that impede the flow of blood through the circulatory system.
Angiography
Medical imaging technique used to visualize the inside, or lumen, of blood vessels and organs of the body, with particular interest in the arteries, veins, and heart chambers.
Computed Tomography
A specialized imaging technique that uses computer-processed combinations of many X-ray measurements taken from different angles to produce cross-sectional images of specific areas of a scanned object.
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