3.6 What can we be confident about? A May 2015 University of Michigan C.S. Mott Children’s Hospital National Poll on Children’s Health reported that 90% of adults are concerned that powdered alcohol will be misused by people under age 21. The margin of error was reported to be 2 percentage points, and the level of confidence was reported to be 95%. This means that
(a) we can be 95% confident that between 88% and 92% of adults are concerned that powdered alcohol will be misused by people under age 21.
(b) we can be 95% confident that between 88% and 92% of adults who were surveyed are concerned that powdered alcohol will be misused by people under age 21.
(c) we know that 90% of adults are concerned that powdered alcohol will be misused by people under age 21.
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(d) Both (a) and (b) above are true.