ECON 261 || WITH ERROR-FREE ANSWERS.
cluster sampling works best correct answers when most of the variation in a population is within
groups and not between groups
Stratified sampling is preferred to cluster sampling when the objective is correct answers to
increase precision
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 correct answers stratified random sampling
variance
Variance
The average of the squared differences from the mean; a common measure of dispersion.
of X⎯⎯⎯ is equal to correct answers Var(X)=σ^2/n
standard error sample mean, computed as correct answers se(X)= σ/√n
the expected value of the sample mean correct answers u
if x is normally distributed with expected value and standard deviation then normally distributed
with correct answers expected value u and standard deviation σ/√n
The central limit theorem states that, for any distribution, as n gets larger, the sampling
distribution of the sample mean becomes- correct answers closer to a normal distribution
The sample size required to approximate the normal distribution depends on correct answers how
much the population varies from normality.
,parameter correct answers constant
statistic correct answers random variable
estimate correct answers particular value of an estimator
when a sample statistic is used to make inferences about a population parameter, it is referred to
as a/an correct answers estimator
The probability distribution of the sample mean is commonly referred to as the correct answers
sampling distribution of x with a line over the top
if we were to sample repeatedly from a given population, the average value of the sample means
will equal correct answers the population mean
a sample statistic is considered biased it correct answers it systematically over- or under-
estimates the unknown parameter being estimated
what is a primary requirement of a "good"' sample? correct answers it is representative of the
population we are trying to describe
selection bias occurs when correct answers there is a systematic exclusion of certain groups from
consideration for the sample
if a sample statistic consistently over- or under-estimates a population parameter, then there is
correct answers bias
What is the characteristic of a "bad" sample correct answers The sample is not representative of
the population we are trying to describe
, which of the following is an example of a population parameter correct answers u
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 correct answers inferential statistics
we use a sample statistic to make inferences about an unknown population correct answers
parameter
Consider a population with a known standard deviation of 16.8. In order to compute an interval
estimate for the population mean, a sample of 51 observations is drawn. correct answers Solution
:
Given that,
a ) Yes, the condition that is normally distribution,
b ) = 16.8
n = 51
At 95% confidence level the z is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0. = 0.025
Z/2 = Z0.025 = 1.960
Margin of error = E = Z/2* (/n)
= 1.960 * (16.)
= 4.61
Margin of error = E = 4.61
C ) n = 251
n = 51
At 95% confidence level the z is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0. = 0.025
cluster sampling works best correct answers when most of the variation in a population is within
groups and not between groups
Stratified sampling is preferred to cluster sampling when the objective is correct answers to
increase precision
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 correct answers stratified random sampling
variance
Variance
The average of the squared differences from the mean; a common measure of dispersion.
of X⎯⎯⎯ is equal to correct answers Var(X)=σ^2/n
standard error sample mean, computed as correct answers se(X)= σ/√n
the expected value of the sample mean correct answers u
if x is normally distributed with expected value and standard deviation then normally distributed
with correct answers expected value u and standard deviation σ/√n
The central limit theorem states that, for any distribution, as n gets larger, the sampling
distribution of the sample mean becomes- correct answers closer to a normal distribution
The sample size required to approximate the normal distribution depends on correct answers how
much the population varies from normality.
,parameter correct answers constant
statistic correct answers random variable
estimate correct answers particular value of an estimator
when a sample statistic is used to make inferences about a population parameter, it is referred to
as a/an correct answers estimator
The probability distribution of the sample mean is commonly referred to as the correct answers
sampling distribution of x with a line over the top
if we were to sample repeatedly from a given population, the average value of the sample means
will equal correct answers the population mean
a sample statistic is considered biased it correct answers it systematically over- or under-
estimates the unknown parameter being estimated
what is a primary requirement of a "good"' sample? correct answers it is representative of the
population we are trying to describe
selection bias occurs when correct answers there is a systematic exclusion of certain groups from
consideration for the sample
if a sample statistic consistently over- or under-estimates a population parameter, then there is
correct answers bias
What is the characteristic of a "bad" sample correct answers The sample is not representative of
the population we are trying to describe
, which of the following is an example of a population parameter correct answers u
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 correct answers inferential statistics
we use a sample statistic to make inferences about an unknown population correct answers
parameter
Consider a population with a known standard deviation of 16.8. In order to compute an interval
estimate for the population mean, a sample of 51 observations is drawn. correct answers Solution
:
Given that,
a ) Yes, the condition that is normally distribution,
b ) = 16.8
n = 51
At 95% confidence level the z is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0. = 0.025
Z/2 = Z0.025 = 1.960
Margin of error = E = Z/2* (/n)
= 1.960 * (16.)
= 4.61
Margin of error = E = 4.61
C ) n = 251
n = 51
At 95% confidence level the z is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0. = 0.025
