Question

A manufacturing company produces electrical insulators. If the insulators break while in use, a short circuit is likely to occur. To test the strength of the insulators, destructive testing is carried out to determine how much force is required to break the insulators. Force is measured by observing the number of pounds of force applied to the insulator before it breaks. Data are available in the worksheet labeled “Problem 1”

1. Construct a 95% confidence interval on population mean force.

2. What assumptions about the population distribution are needed in order for the procedures above to be valid?

3. Construct the appropriate plot(s) to evaluate the assumptions made in part (3) above. Do you think the assumptions are valid? Explain.

Problem 1 Data Set

Observation	Force (lbs)
1	1870
2	1866
3	1820
4	1728
5	1764
6	1744
7	1656
8	1734
9	1788
10	1610
11	1662
12	1688
13	1634
14	1734
15	1810
16	1784
17	1774
18	1752
19	1522
20	1550
21	1680
22	1696
23	1756
24	1810
25	1592
26	1762
27	1652
28	1662
29	1866
30	1736

Answer 1

1)

1)

2) We assume that the sample is drawn using simple random sampling .

Each sample is independent of the other.

The sample is drawn from a population that is approximately normally distributed.

3) We will draw a NORMAL Q-Q plot to see if our assumption of NORMALITY is satisfied

most of the points are allighned near to the line, which suggest that the data is approximately normal, though slight skewness can be seen but it is approximately normal.