Question

A manufacturing company produces electric insulators. You define the variable of interest as the strength of the insulators. If the insulators break when in​ use, a short circuit is likely. To test the strength of the​ insulators, you carry out destructive testing to determine how much force is required to break the insulators. You measure force by observing how many pounds are applied to the insulator before it breaks. The accompanying data represent the amount of force required to break a sample of 30 insulators. Complete parts​ (a) through​ (c) below. LOADING... Click the icon to view the data.

a. Construct a 99​% confidence interval for the population mean force. nothingless than or equalsmuless than or equals nothing ​(Round to the nearest integer as​ needed.)

b. What assumption must you make about the population distribution in order to construct the confidence interval estimate in​ (a)?

A. The population distribution is unimodal and not extremely skewed.

B. The population standard deviation is known.

C. The population distribution is not normally distributed.

D. The population distribution is uniformly distributed. c.

Do you think that the assumption needed in order to construct the confidence interval estimate in​ (a) is​ valid? Explain. The assumption is ▼ in serious doubt reasonable for n equals nothing since ▼ an appropriate plot shows that the sample distribution is not uniformly distributed. the population standard deviation is known. an appropriate plot shows that the sample distribution is uniformly distributed. the population standard deviation is not known. an appropriate plot shows that the sample distribution is not extremely skewed. the sample size is less than 30. the sample size is at least 30. an appropriate plot shows that the sample distribution is highly skewed.

1863
1706
1663
1628
1621
1775
1585
1658
1578
1651
1889
1799
1709
1675
1722
1781
1788
1767
1797
1877
1838
1710
1786
1708
1827
1799
1692
1836
1665
1714

Answer 1

From the above plot, the assumption normality on the sample satisfied. Hence, we think that the assumption needed in order to construct the confidence interval estimate in​ (a) is​ valid.