SSGI SixSigma Black Belt: Chp 12 Quiz

The mean of a process is 10. The standard deviation is 5. The sample size is 25. What is the upper control limit?

13 => 10 + 3(5/5)

A process has a mean of 35.0. The standard deviation is 5.00. If the sample size is 49, what is the upper control limit?

37.1428 => 35 + 3(5/7)

When you ask employees in a company cafeteria to fill out a questionnaire on employee morale this would be an example of __________ sampling.

Convenience

Which of the following is not an approach to probability sampling?

Convenience

The standard deviation measures the variation in a population distribution, but the standard error of the mean measures the variation in the _____________ .

Distribution of sample means

A population is a subset of a sample.

False

A sample of fifteen patients are selected from all patients at a health clinic. The average satisfaction is 85. Another sample taken of fifteen patients at the same time should also have a sample mean of 85.

False

According to the central limit theorem, when sample sizes are large the distribution of sample means will not be normally distributed around the population mean.

False

In Systematic Sampling the population is divided into clusters and then randomly sampled.

False; In Systematic Sampling every nth unit is sampled. Clusters are not used.

Cluster sampling cannot be classified as random sampling.

False; It is considered random sampling provided that random sampling is exercised within the cluster.

When the sample size is large, it is very likely that a single sample mean will be in the tails of the distribution of sample means.

False; It will be close to the mean of the distribution of sample means (population mean)

An upper control limit, when large samples are taken, will be positioned at plus three standard deviations.

False; Plus three standard errors of the mean.

All subgroups can be classified as rational subgroups.

False; The data in rational subgroups must be generated under the same set of conditions.

If you sample patients from two health care clinics located in separate towns but affiliated with the same hospital, and then combine the samples, the group would be classified as a rational subgroup.

False; The result from each clinic should be separated into two groups. They would then be classified as rational subgroups.

In a rational subgroup the variation of the data within a subgroup must be greater than the variation between the subgroups.

False; The reverse is true. The variation within the subgroups would be less than the variation between subgroups.

What is the likelihood that a sample mean will fall between plus and minus two standard errors of the mean from the mean of the distribution of sample means?

95%

A population includes all members of a defined group that is being studied.

True

All rational subgroups can be considered subgroups but not all subgroups can be classified as rational subgroups.

True

Consider that a sample of n=35 is taken from a large population. It is very unlikely that a second sample of n=35, and taken from the same population, will have the same mean as the first sample.

True

In Stratified Random Sampling the results from each strata are then combined and weighted in relation to the size of the strata from which they were taken.

True

In the sampling process, a single sample is taken, its mean computed, and the mean plotted on a control chart.

True

Sample means cluster around the mean of the population.

True

The mean of the distribution of sample means is the same as the mean of the population from which those samples were taken.

True

The sampling distribution of the mean, since it is normally distributed for large samples, will have the same special properties as does the population distribution. For example, 68 percent of all observations will fall between plus and minus one standard error of the mean.

True

When large sample sizes are taken from a uniform distribution the sampling distribution will be normally distributed.

True

When samples of size n are taken from a population, every sample mean will vary from the other sample means.

True