IS 242 Chapter 7: Sampling and Sampling Distributions

A _____ consists of all items of interest in a statistical problem.

population

If we were to sample repeatedly from a given population, the average value of the sample means will equal the

population mean

When a firm applies statistical techniques to develop and maintain its ability to produce high-quality goods and services, it is implementing statistical _____ _____.

quality control

X is a _______ variable.

random

A statistic is a _____ _____ whose value depends on the chosen random sample.

random variable

The probability distribution of the sample mean is commonly referred to as the _____.

sampling distribution of x

Assignable variation is caused by

specific events that can usually be identified and eliminated.

In ______, the population is divided up into mutually exclusive and collectively exhaustive groups called strata. The sample consists of randomly-selected elements from each stratum.

stratified random sampling

The CLT states that the ______ of a large number of independent observations from the same underlying distribution has an approximate normal distribution.

sum

A ______ is representative of sample data.

survey

The standard deviation of X is calculated as

the positive square root of the variance of X

Bias can occur in sampling. Bias refers to

the tendency of a sample statistic to systematically over- or underestimate a population parameter

Selection bias occurs when

there is a systematic exclusion of certain groups from consideration for the sample.

Nonresponse bias occurs when

those responding to a survey or poll differ systematically from the non-respondents.

Stratified sampling is preferred to cluster sampling when the objective is

to increase precision.

P is an ______ estimator of p.

unbiased

This type of chart monitors the central tendency of a production process.

x chart

Which of the following is an example of a population parameter?

μ

The standard deviation of the sampling distribution of X is calculated as _______.

σ / √n

When the finite population correction factor is applied to the sample mean, the resulting standard error for the sample mean is equal to

σ / √n √ N-n / N-1.

The standard deviation of P equals

√p(1−p)/n

According to the CLT, as the population proportion deviates from p = ________, we need a larger sample size for the approximation.

0.50

A population has a mean of 100 and a standard deviation of 10. A random sample of 25 is selected. The expected value of X is equal to ______.

100

In general, the control limits of a control chart are set at ______ standard deviations from the centerline.

3

The general rule for using the finite correction factor is that the sample constitutes at least ______ percent of the population.

5

______ variation in the production process is caused by specific events or factors that can usually be identified and eliminated.

Assignable

______ variation is caused by a number of randomly occurring events that are part of the production process.

Chance

______ variation is not generally considered to be under the control of the individual worker or machine.

Chance

______ sampling is preferred when the objective is to reduce costs.

Cluster

A parameter is a numerical measure that describes a sample.

False

A production process is in control if the sample means on a control chart start below the centerline, trend upward, and do not cross the upper control limit.

False

This type of chart monitors the variability of a production process.

R chart

What kind of sampling is more likely to be used by political pollsters who want to ensure that each religious group is represented in the sample?

Stratified random sampling

Which of these is a characteristic of a "bad" sample?

The sample is not representative of the population we are trying to describe.

______ = X − μ / σ/√n

Z

If X is normally-distributed, we can transform X into the standard normal random variable as

Z = X − μ / σ / n√

In general, two approaches are used for statistical quality control. They are the ______ sampling and the ______ approach.

acceptance, detection

In a statistical problem, a population consists of

all items of interest.

If the population from which the sample is drawn is normally distributed, then the sampling distribution of the sample mean is

always normally distributed.

The firm wants to identify and correct ______ variations in the production process.

assignable

The tendency of a sample statistic to systematically overestimate or underestimate a population parameter is known as

bias

When the information from a sample is not typical of information in the population in a systematic way, we say that ________ has occurred.

bias

A ______ is representative of population data.

census

The ______ represents the variable's expected value when the production process is in control.

centerline

A theorem that allows us to use the normal probability distribution to approximate the sampling distribution of the sample mean whenever the sample size is large is known as the _____ _____ _____.

central limit theorem

A parameter is a _______ , although its value may be unknown.

constant

When a firm inspects the production process to determine at which point the process does not conform to standards, it is applying the ______ approach for statistical quality control.

detection

A particular value of an estimator is called an

estimate

When a sample statistic is used to make inferences about a population parameter, it is referred to as an

estimator

If X is normally distributed with expected value μ and standard deviation σ, then X is normally distributed with:

expected value μ and standard error σ / √n.

The factor N−n / N−1 is called the _____ ____ _____ factor.

finite population correction

The sample size required to approximate the normal distribution depends on

how much the population varies from normality.

The further a population proportion deviates from p = 0.50, the _______ the sample size required in order to satisfy a normal approximation.

larger

The purpose of statistical quality control is to

maintain high-quality goods and services.

Control charts were created to

monitor the behavior of a production process.

As the sample size increases, the shape of the sampling distribution of P becomes

more normal.

We can use the finite population correction factor when

n ≥ 0.05N.

As a general guideline, the normal distribution approximation can be used to describe the sampling distribution of the sample mean when

n ≥ 30.

The value of the finite population correction factor is always less than

one