# Statistics Question 3

**Question description**

From historical data you know that the time it takes to do a
certain job is normally distributed with a mean of 130 minutes and a standard deviation
of 20 minutes. To monitor performance, each week
a sample of 25 jobs is selected and the average
time it takes to do the job is recorded. In a particular week the average time to
do the job was 128 minutes with a standard deviation of 16 minutes. The distribution
of times in the sample comes out bell-shaped. What can you say, if anything,
about each of the following intervals: (a) 128 ± 2 x 16, (b) 130 ± 2 x (20/√25), (c) 128 ± 2 x (16/√25),
(d) 128 ± 2 x (20/√25).

## Tutor Answer

## 5 Reviews

**Quality**

**Communication**

**On Time**

**Value**

Brown University

1271 Tutors

California Institute of Technology

2131 Tutors

Carnegie Mellon University

982 Tutors

Columbia University

1256 Tutors

Dartmouth University

2113 Tutors

Emory University

2279 Tutors

Harvard University

599 Tutors

Massachusetts Institute of Technology

2319 Tutors

New York University

1645 Tutors

Notre Dam University

1911 Tutors

Oklahoma University

2122 Tutors

Pennsylvania State University

932 Tutors

Princeton University

1211 Tutors

Stanford University

983 Tutors

University of California

1282 Tutors

Oxford University

123 Tutors

Yale University

2325 Tutors