Question

Why is it important to compute confidence intervals for
estimates of population means or percentages?

A. Because every sample statistic is subject to error.

B. Because managers don’t like point estimates.

C. Because every sample statistic must be presented without
error.

D. Because the sample statistic = the population parameter.

The calculated z or t value is inversely related to the size of
the differences between two means or percentages (i.e., as the
difference between two means or percentage increases, the
calculated z or t decreases.

A. True

B. False

The calculated z or t value is inversely related to the size of
the standard error (i.e., as standard error of the mean or
percentage increases, the calculated z or t decreases.

A. True

B. False

Answer #1

The confidence interval provides a range of values in which sample statistics can lie so it is better than point estimate. Sample statistics provides an estimate to po;ulation parameter. It is not always equal to population parameter.

Correct option is

A. Because every sample statistic is subject to error.

------------------------------------------------------

In calculating z or t value, the difference between two means or percentage comes into numerator so as the difference increase value of z or t will also increase.

Hence, correct option is

B: False

------------------------------------------------------

In calculating z or t value, the standard error comes into denominator so as the standard error increases value of z or t will decreases.

Hence, correct option is

A. True

1.
The confidence intervals for the population proportion are
generally based on ________.
the t distribution when the population standard deviation is not
known
the z distribution
the t distribution
the z distribution when the sample size is very small
2.
The difference between the two sample means 1
– 2 is an interval estimator of the difference
between two population means μ 1 – μ 2.
True
False
3.
Excel does not have a special function that allows to
calculate t values.
True...

Consider the following statements concerning confidence interval
estimates:
A. The use of the pooled variance estimator when constructing a
confidence interval for the difference between means requires the
assumption that the population variances are equal.
B. The width of a confidence interval estimate for the proportion,
or for mean when the population standard deviation is known, is
inversely proportional to the square root of the sample size.
C. To determine the sample size required to achieve a desired
precision in...

True or False?
1. σM equals the standard deviation
divided by the square root of the sample size
2. Larger samples more accurately reflect the population than
smaller samples
3. If n = 1, the standard error will equal the standard
deviation of the population
4. If a population is skewed, the distribution of sample means
will never be normal
5. The mean for the distribution of samples means is equal to
the mean of the population
6. As the sample...

1. The 95% confidence interval states that 95% of the sample
means of a specified sample size selected from a population will
lie within plus and minus 1.96 standard deviations of the
hypothesized population mean. T or F
2. Which of the following is NOT necessary to determine how
large a sample to select from a population?
Multiple Choice
The level of confidence in estimating the population
parameter
The size of the population
The maximum allowable error in estimating the...

Indicate whether the following statement is true or false.
1. When estimating a confidence interval for the difference
between the means of two independent populations, the pooled
variance is the average of two sample variances, if the two sample
sizes are equal.
2. Both the t-distribution and standard normal distribution have
the same mean, but the t-distribution has a smaller standard
deviation than the standard normal distribution.
3. The standard deviation of the distribution
of (i.e. standard error of the mean)...

The margin of error for a confidence interval for a population
is equivalent to the standard deviation times the z-score value, or
t-score value depending on the size of the population, for the
probability of interest times the standard deviation of the
population. True or False

In testing the difference between two population means using two
independent samples, the population standard deviations are assumed
to be unknown, each sample size is 30, and the calculated test
statistic z = 2.56. If the test is a two-tailed and the 5% level of
significance has been specified, the conclusion should be:
a.
none of these answers is correct.
b.
choose two other independent samples.
c.
reject the null hypothesis.
d.
not to reject the null hypothesis.

8. Confidence intervals for estimating the difference in
population means
Elissa Epel, a professor of health psychology at the University
of California–San Francisco, studied women in high- and low-stress
situations. She found that women with higher cortisol responses to
stress ate significantly more sweet food and consumed more calories
on the stress day compared with those with low cortisol responses,
and compared with themselves on lower stress days. Increases in
negative mood in response to the stressors were also significantly...

Answer the following about T-Test & T-distributions:
1. Which of the following statements related to the
t-distribution is not true?
Select one:
a. Since the population standard deviation is usually unknown,
the standard error of the sample mean is estimated using the sample
standard deviation as an estimator for the population standard
deviation. The formula is s/sqrt(n).
b. The population must be t-distributed in order to use the
t-distribution.
c. Like the Normal distribution, the t-distribution is symmetric
and unimodal....

1. what effect does increasing the sample size have on the
population standard deviation?
If the sample size increases then the sample standard deviation
will be decreases. But in this sentence, it is not a sample
standard deviation. Every answer in CheggStudy is decrease.
I think sample size doesn't affect to the population standard
deviation.
2. When performing a hypothesis test, what effect does
increasing the sample size have on the probability of type 1
error?
3. When performing a...

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