8.1
15
x̄ is approximately normal with u/x= 80, σx̅=2
0.0668
0.0179
0.7969
17
The population must be normally distributed to compute probabilities involving the sample mean.
0.7486
0.4052.
19
0.3520
The sampling distrbiution of x bar is normal with ux= 266 and standard deviation x bar= 3.578.
0.0465
0.0040.
Unusual because the sample likely came from a population whose mean gestation period is less than 266 days.
0.9844.
21
0.3085.
0.418.
0.0071.
Increasing the sample size decreases p(xbar >95). This happens because standard deviation x bar decreases as n increases.
A mean reading rate of 92.8 wpm is not unusual since p(xbar> or equal to 92.8) = 0.1056
There is a 5% chance that the mean reading speed of a random sample of 20 second grade students will exceed 93.7 words per minute.
23
0.5675.
0.7291.
0.8051.
0.8531.
The likelihood of earning a positive rate of return increases as the investment time horizon increases.
8.2
11
The sampling distribution of p hat is approximately normal with up= 0.8 and op= 0.046
0.1922
0.047.
12
The sampling distribution of p hat is approximately normal with up= 0.65 and op= 0.0337.
0.1867.
0.0375.
13
The sampling distribution is approximately normal with up= 0.35 and op= 0.015.
0.0040.
0.0233.
14
The sampling distribution of p hat is approximately normal with up= 0.42 and op= 0.0129.
0.0099.
0.606.
15
Qualitative.
The source of the variability is the individuals being surveyed and whether they can order a meal in a foreign language.
The sampling distribution of p hat is normal with up=0.47 and op= 0.035.
0.1977.
0.0239.
16
Qualitative.
The source of the variability are the individuals being surveyed and whether they are satisfied with the way things are going in their life.
0.0384.
0.2177.
0.0344 –> unusual.
17
The sampling distribution of p hat is approximately normal with up= 0.39 and op=0.022
0.3228.
0.3198.
0.0838.