Page 444 - Six Sigma Demystified

424 Six SigMa DemystifieD

60. When using process capability estimates,
A. the process must be in control, or the estimate is misleading.
b. always estimate the process using sample sigma.
c. we should sort the data prior to analysis.
d. All the above are true.
61. A 90% confidence interval for the mean is from 13.8067 to 18.1933. This means that
A. there is a 90 percent probability that the true mean lies between 13.8067 and
18.1933.
b. 90 percent of all values in the population lie between 13.8067 and 18.1933.
c. 90 percent of all the sample values in the population lie between 13.8067 and
18.1933.
d. All the above are true.
62. Assuming normality, the two-sided 95% confidence interval on the mean for a
sample of 20 units with an average of 121 and a standard deviation of 15 is
A. (112.8, 129.2).
b. (114.0, 128.0).
c. (115.2, 126.8).
d. (114.4, 127.6).

63. Assuming normality, the one-sided upper 95% confidence interval on the mean
for a sample of 20 units with an average of 121 and a standard deviation of 15 is
A. 129.2.
b. 128.0.
c. 126.8.
d. 127.6.

64. For a sample of 20 units with an average of 121 and a standard deviation of 15, a two-
sided hypothesis that the mean equals 115 (assuming normality) yields a result of
A. reject the null hypothesis that the mean equals 115 because the p value is less
than 0.05.
b. reject the null hypothesis that the mean equals 115 because the p value is greater
than 0.05.
c. assert that the mean equals 115 because the p value is greater than 0.05.
d. The mean may or may not equal 115; we cannot reject the hypothesis that the
mean equals 115 because the p value is greater than 0.05.
65. For a sample of 20 units with an average of 121 and a standard deviation of 15,
for an alternative one-sided hypothesis that the mean is greater than 115
(assuming normality), we should
A. reject the null hypothesis that the mean is less than or equal to 115 and assert it
is greater than 115 because the p value is less than 0.05.
b. reject the null hypothesis that the mean is less than or equal to 115 and assert
that it is greater than 115 because the p value is greater than 0.05.
c. reject the null hypothesis that the mean is greater than or equal to 115 and assert
that it is less than 115 because the p value is greater than 0.05.
d. The mean may or may not be greater than 115; we cannot reject the hypothesis
that the mean is less than or equal to 115 because the p value is greater than 0.05.