1. Arandomsample of size n = 19 is drnwn from a normal distribution for which a2 = 12.0. In what range are we likely to find the sample variance, s2? Answer the question by finding two numbers a and b such that
P(a s s2
b) = 0.95
2. One of the occupational hazards of being an airplane pilot is I.he hearing loss that results from being exposed to high noise levels. To document the magnitude of the problem, a team of researchers measured the cockpit noise levels in 18 commercial aircraft. The results (in decibels) are as follows (94).
|
Plane
1
|
Noise Level
74
|
Plane
10
|
Noise Level
72
|
|
2
|
77
|
11
|
90
|
|
3
|
80
|
12
|
87
|
|
4
|
82
|
13
|
73
|
|
5
|
82
|
14
|
83
|
|
6
|
85
|
15
|
86
|
|
7
|
80
|
16
|
83
|
|
8
|
75
|
17
|
83
|
|
9
|
75
|
18
|
80
|
(ii) Assume that cockpit noise levels are normally distributed. Use Theorem 7.5.1 to construct a 95% confidence interval for the standard deviation of noise levels ftom plane to plane.
(b) Use these same data lo construct two one-sided 95% confidence intervals for a.