How accurate are radon detectors of a type sold to homeowners? Toanswer this question, university researchers placed 12 detectors ina chamber that exposed them to 105 picocuries per liter (pCi/l) ofradon. ^15 The detector readings were as follows:

91.9, 97.8, 111.4, 122.3, 105.4, 95.0, 103.8, 99.6, 96.6,119.3, 104.8, 101.7

1) Give a 90% confidence interval for the mean reading.

2) Is there sufficient evidence that, at 10%, the mean differs from 105?