isds reading ch 7
As the population proportion deviates from p = 0.50, what happens to the sample size required in order to satisfy a normal approximation?
It gets larger.
True or false: If we had access to data that included the entire population, then the values of the parameters would be known and no statistical inference would be required.
True Rationale: If you have data that describes the entire population, then the answers are perfect and no sampling or estimation is needed.
Which of the following statements is MOST accurate?
A parameter is a constant although its value may be unknown.
Bias can occur in sampling. Bias refers to
the tendency of a sample statistic to systematically over- or under-estimate a population parameter.
Selection bias occurs when
there is a systematic exclusion of certain groups from consideration for the sample.
When a sample statistic is used to make inferences about a population parameter, it is referred to as a/an
estimator.
We can use the finite population correction factor when
n ≥ 0.05N.
The general rule for using the finite correction factor is that the sample constitutes at least _____ of the population.
5%
In any production process, variation in the quality of the end product is inevitable. Chance variation, or common variation, refers to
A number of randomly occurring events that are part of the production process.
Which of the following are true about the standard deviation of the sample mean? Select all that apply.
Another name for the standard deviation of the sample mean is the the standard error of the sample mean. The less variability there is in the population, the less variability there will be in the sample means.
As the sample size increases, what happens to the standard deviation of X ?
It gets smaller.
Which of the following are components of a control chart? Select all that apply.
Lower control limit (LCL) Upper control limit (UCL) Centerline
True or false: Most statistical methods presume simple random samples.
True
In general, the two approaches that are used for statistical quality control are
acceptance sampling and the detection approach.
We use the finite population correction factor to
reduce the sampling variation of X and P .
Assignable variation is caused by
specific events that can usually be identified and eliminated.
The standard deviation of the sampling distribution of X is calculated as ______.
σ/√n
The standard deviation of P equals
√p(1−p)/n
If X is normally distributed with expected value μ and standard deviation σ, then X is normally distributed with
expected value μ and standard deviation σ/ √n .
When a firm inspects the production process to determine at which point the process does not conform to standards, it is applying ______ for statistical quality control.
the detection approach
If we were to sample repeatedly from a given population, the average value of the sample means will equal
the population mean.
Stratified sampling is preferred to cluster sampling when the objective is
to increase precision.
The branch of statistics that uses sample statistics to estimate a population parameter or test a hypothesis about such a parameter is BEST referred to as ________.
inferential statistics
A firm uses acceptance sampling when
it produces a product and at the end of the process, inspects a portion.
The purpose of statistical quality control is to
maintain high-quality goods and services.
The expected value of X is equal to ______.
μ
In general, the control limits of a control chart are set at ______ standard deviations from the centerline.
3
________ is caused by a number of randomly occurring events that are part of the production process.
Chance variation
The sample size required to approximate the normal distribution depends on
how much the population varies from normality.
Control charts were created to
monitor the behavior of a production process.
As a general guideline, the normal distribution approximation can be used to describe the sampling distribution of the sample mean when
n ≥ 30.
We use a calculated sample ______ to make inferences about an unknown population ______.
statistic, parameter
Cluster sampling works best
when most of the variation in a population is within groups and not between groups.
The expected value of P is the
proportion of successes in the population.
The probability distribution of the sample mean is commonly referred to as the _____.
sampling distribution of x (with the line over it)
Which of the following is an example of a sample statistic?
x (with line above it)
Which of the following is considered an estimate?
x = 20
True or false: A process could be veering out of control if there is a trend within the upper and lower control limits of a control chart.
True
A manufacturing production process is in control if the sample means are
randomly spread out between the control limits.
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 expected value of X (with line over it) is equal to ______.
μ
If X is normally-distributed, we can transform X into the standard normal random variable as
Z = X−μ/σ√n
In statistical quality control, a tool used to monitor the behavior of a production process over time is called
a control chart.
A variation in production caused by a specific event or factor that can usually be identified and eliminated is called
assignable variation.
When a sample of n observations that has the same probability of being selected from the population as any other sample of n observations is called a ______.
simple random sample
When a voter provides incorrect answers to a survey or poll because they think that others will look unfavorably on their choices, this is referred to as __________ -desirability bias.
social
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 central limit theorem states that as n gets larger, the sampling distribution of the sample proportion
approaches a normal distribution.
Which one of the following is true about stratified and cluster sampling?
Stratified sampling provides greater precision.
Which of these is a characteristic of a "bad" sample?
The sample is not representative of the population being studied.
Which of the following statements is MOST accurate?
A statistic is a random variable whose value depends on the chosen random sample.
_________ involves dividing a population into mutually exclusive and exhaustive groups, and then selecting a random sample from these groups for analysis.
Cluster sampling
What is a primary requirement of a "good" sample?
It is representative of the population we are trying to describe.
A population consists of all items of interest in a statistical problem, whereas a ______ is a subset of the population.
sample
In ______, the population is divided up into strata and then randomly selected observations are taken proportionately from each stratum.
stratified random sampling
Nonresponse bias occurs when
those responding to a survey or poll differ systematically from the non-respondents.
When the finite population correction factor is applied to the sample proportion, the resulting standard error for the sample proportion is equal to
√p(1−p)/n × √(N−n)/(N−1) .
A sample is
a subset of the population
A particular value of an estimator is called a/an _______.
estimate
A sampling distribution (select all that apply)
is the same as the probability distribution for a statistic. is distribution of a statistic that is calculated from all possible samples of size n from a population.
A sample statistic is considered biased if
it systematically over- or under-estimates the unknown parameter being estimated.
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
Social-desirability bias exists when
opinions that are socially unacceptable are not expressed.
The control limits for a P chart are defined as
p ± 3 √p(1−p)n
Which of the following is an example of a population parameter?
μ
For an X chart, control limits are calculated as
μ ± 3 σ/√n
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
In a statistical problem, a population consists of
all items of interest.