Chapter 11: Inferences About Population Variances

The sampling distribution used when making inferences about a single population variance is the
1. t distribution with (n - 1) degrees of freedom
2. chi-square distribution with (n - 1) degrees of freedom
3. F distribution with (n - 1) degrees of freedom for the numerator and (n - 1) degrees of freedom for the denominator
4. none of the above
The sampling distribution of the ratio of two independent sample variances extracted from normal populations with equal variances is the
1. t distribution
2. chi-square distribution
3. F distribution
4. normal distribution
5. none of the above
with 20 degrees of freedom is
1. 28.412
2. 27.204
3. 11.651
4. 12.443
5. none of the above
To avoid the problem of not having access to tables of F distribution with values given for the lower tail when a two-tailed test is required, let the sample with the smaller sample variance be
1. the numerator of the test statistic
2. the denominator of the test statistic
3. It makes no difference how the ratio is set up
4. none of the above
A sample of 20 cans of tomato juice showed a standard deviation of 0.4 ounces. A 95% confidence interval estimate for the variance of the population is
1. 0.2313 to 0.8533
2. 0.2224 to 0.7924
3. 0.0889 to 0.3169
4. 0.0925 t0 0.3413
A process is in control if the maximum variance is .05. Assume that the population is normally distributed. A sample of size 26 showed a sample variance of .06. Is the process in control?
5. none of the above
A process is in control if the maximum variance is .05. Assume that the population is normally distributed. A sample of size 26 showed a sample variance of .06. the value of the test statistic is
1. 104
2. 20.83
3. 37.65
4. 26.00
5. none of the above
A process is in control if the maximum variance is .05. Assume that the population is normally distributed. A sample of size 26 showed a sample variance of .06. The critical value at 95% confidence is
1. 14.611
2. 15.379
3. 37.652
4. 38.885
5. none of the above
The F.05 value with 20 numerator degrees of freedom and 30 denominator degrees of freedom is
1. 1.93
2. 1.94
3. 2.20
4. 2.55
5. none of the above
. A sample of 40 items from population 1 has a sample variance of 8 while a sample of 60 items from population 2 has a sample variance of 10. If we test whether the variances of the two populations are equal, the test statistic will have a value of
1. 0.8
2. 1.56
3. 1.5
4. 1.25
5. none of the above