An electrical firm manufactures light bulbs that have a length of life that is approximately
normally distributed with a standard deviation of 40 hours. A sample of 30 bulbs has an
average life of 780 hours.
An electrical firm manufactures light bulbs that have a length of life that is approximately
normally distributed with a standard deviation of 40 hours. A sample of 30 bulbs has an
average life of 780 hours.
What is the most sampling error at 95% confidence interval?
4
8
14
28
An electrical firm manufactures light bulbs that have a length of life that is approximately
normally distributed with a standard deviation of 40 hours. A sample of 30 bulbs has an
average life of 780 hours.
How large a sample is needed if we wish to be 95% confident that our sample mean
will be within 10 hours of the true mean?
245
6
68
62
An electrical firm manufactures light bulbs that have a length of life that is approximately
normally distributed with a standard deviation of 40 hours. A sample of 30 bulbs has an
average life of 780 hours.
What will the sampling error if we increase confident form 95% to 96%?
No change
Increase
Decrease
Uncertain
What is the approximate pooled standard deviation if we assume that two populations
have equal variance?
7.83
3.96
4.57
1.78
What is value of the test statistic t ?
1.094
1.636
2.796
4.228
What is the β risk if the true mean is 69 kilograms and sample size n = 36 ?
0.3264
0.1587
0.4840
0.6736
If we wish to decrease the β risk, we may
increase the sample size
decrease the sample size
decrease α risk
change statistics
Find the sample size required if the power of our test is to be 0.95 when the true mean
is 69 kilograms.
98
72
143
271
Which test statistic are you going to use in this test?
t statistic
Z statistic
F statistic
What the critical value of this test?
2.571
1.96
7.378
11.143
What will you conclude?
Night shift has higher defective rate than the other two.
All shifts have no significant difference.
All shifts have significant differences.
Information is not sufficient to do any conclusion.
One positive, two negative.
Two positive, one negative.
All positive.
All negative.
可觀看題目詳解,並提供模擬測驗!(免費會員無法觀看研究所試題解答)