Researchers tested patients with cardiac pacemakers to see if use of a cellular telephone interferes with the

Question:

Researchers tested patients with cardiac pacemakers to see if use of a cellular telephone interferes with the operation of the pacemaker. There were 959 tests conducted for one type of cellular telephone; interference with the pacemaker (detected with electrocardiographic monitoring) was found in 15.7% of these tests.18
(a) Use these data to construct an appropriate 90% confidence interval.
(b) The confidence interval from part (a) is a confidence interval for what quantity? Answer in the context of the setting.