Homework Soursea hard drive manufactorer would like to ensure that the mean
a hard drive manufactorer would like to ensure that the meantime between failures for its new hard drive is 1 million hours. a stress test is designed that can stimulate the work load at a much faster pace. the testers assume that a test lasting 10days correlates with failure times exceedig the 1-million hour mark. in stress tests of 15 hard drives they found an average of 9.5 days, with a standard deviation of 1 day. does 90% confidence level include 10 days?
find the 80% and 90% confidence interval for a survey with n=100 and p=o.45
Solution
a hard drive manufactorer would like to ensure that the meantime between failures for its new hard drive is 1 million hours. a stress test is designed that can stimulate the work load at a much faster pace. the testers assume that a test lasting 10days correlates with failure times exceedig the 1-million hour mark. in stress tests of 15 hard drives they found an average of 9.5 days, with a standard deviation of 1 day. does 90% confidence level include 10 days?
Confidence Interval Estimate for the Mean
Data
Sample Standard Deviation
1
Sample Mean
9.5
Sample Size
15
Confidence Level
90%
Intermediate Calculations
Standard Error of the Mean
0.2582
Degrees of Freedom
14
t Value
1.7613
Interval Half Width
0.4548
Confidence Interval
Interval Lower Limit
9.05
Interval Upper Limit
9.95
90% CI = (9.05, 9.95)
This 90% confidence level does not include 10 days.
find the 80% and 90% confidence interval for a survey with n=100 and p=o.45
Confidence Interval Estimate for the Proportion 80%
Data
Sample Size
100
Number of Successes
45
Confidence Level
80%
Intermediate Calculations
Sample Proportion
0.45
Z Value
1.282
Standard Error of the Proportion
0.0497
Interval Half Width
0.0638
Confidence Interval
Interval Lower Limit
0.3862
Interval Upper Limit
0.5138
80% CI =(0.3862, 0.5138)
Confidence Interval Estimate for the Proportion 90%
Data
Sample Size
100
Number of Successes
45
Confidence Level
90%
Intermediate Calculations
Sample Proportion
0.45
Z Value
1.645
Standard Error of the Proportion
0.0497
Interval Half Width
0.0818
Confidence Interval
Interval Lower Limit
0.3682
Interval Upper Limit
0.5318
90% CI =(0.3682, 0.5318)
| Confidence Interval Estimate for the Mean | |
| Data | |
| Sample Standard Deviation | 1 |
| Sample Mean | 9.5 |
| Sample Size | 15 |
| Confidence Level | 90% |
| Intermediate Calculations | |
| Standard Error of the Mean | 0.2582 |
| Degrees of Freedom | 14 |
| t Value | 1.7613 |
| Interval Half Width | 0.4548 |
| Confidence Interval | |
| Interval Lower Limit | 9.05 |
| Interval Upper Limit | 9.95 |
