Confidence interval
The data table below provides cost overruns (actual costs minus estimated costs) in thousands of dollars on similar-size engineering projects completed this year. Calculate the following:
a. A 95 percent confidence interval for the average overrun this process would deliver over a long time period, assuming it is stable.
a. A 99 percent confidence interval for the same average.
Explain why this is a different width than the 95 percent interval.
|
-16
|
-480
|
-222
|
|
-404
|
-77
|
-76
|
|
-397
|
221
|
-427
|
|
113
|
93
|
-268
|
|
-791
|
107
|
-230
|
|
-165
|
-272
|
287
|
|
-118
|
133
|
-285
|
|
9
|
276
|
-344
|
|
-651
|
36
|
-394
|
|
383
|
-298
|
161
|