Question

- For the standard normal distribution, compute Z
_{0.69}. Use Excel and round the answer to two decimal places. - Consider the following test performed with the level of
significance 0.01: A random sample of size 28 is obtained from a
normally distributed population. The population standard deviation
is equal to 3.6. The sample mean happened to be 24. For this
hypothesis test, what will be
*the critical value (the relevant z-alpha)*? Round the answer to three decimal places. - A probability distribution of all possible sample proportions of a given sample size is called the sampling distribution of the sample ----------
- Select the false statement.

a. When t-numbers are used for computing the width of a confidence interval, the corresponding Student's t-distribution follows (n-1) degrees of freedom, where n is the sample size.

b. One should use z-numbers when estimating the population proportion.

c. When one knows the standard deviation of the population, one must use t-numbers to determine the width of a confidence interval.

d. If all other relevant variables are kept the same, than the bigger the sample size, the narrower the confidence interval is.

Answer #1

True or false:
1. When constructing a confidence interval for a sample
Mean, the t distribution is appropriate whenever the sample size is
small.
2. The sampling distribution of X (X-bar) is not always
a normal distribution.
3. The reason sample variance has a divisor of n-1
rather than n is that it makes the sample standard deviation an
unbiased estimate of the population standard
deviation.
4. The error term is the difference between the actual
value of the dependent...

1. Find the area under the standard normal curve (round to four
decimal places)
a. To the left of z=1.65
b. To the right of z = 0.54
c. Between z = -2.05 and z = 1.05
2. Find the z-score that has an area of 0.23 to its right.
3. The average height of a certain group of children is 49
inches with a standard deviation of 3 inches. If the heights are
normally distributed, find the probability that a...

Consider a normal population with an unknown population standard
deviation. A random sample results in x−x− = 62.88 and
s2 = 16.81. [You may find it useful to
reference the t table.]
a. Compute the 90% confidence interval for
μ if x−x− and s2 were obtained from a
sample of 24 observations. (Round intermediate calculations
to at least 4 decimal places. Round "t" value to 3 decimal
places and final answers to 2 decimal places.)
b. Compute the 90% confidence...

Use the standard normal distribution or the t-distribution to
construct a 99% confidence interval for the population mean.
Justify your decision. If neither distribution can be used,
explain why. Interpret the results. In a random sample of 13
mortgage institutions, the mean interest rate was 3.59% and the
standard deviation was 0.42%. Assume the interest rates are
normally distributed.
Select the correct choice below and, if necessary, fill in any
answer boxes to complete your choice.
A. The 99% confidence...

When, if ever, is it appropriate to use the standard normal
distribution as a substitute for the t distribution with n – 1
degrees of freedom in estimating a population mean?

When, if ever, is it appropriate to use the standard normal
distribution as a substitute for the t distribution with n – 1
degrees of freedom in estimating a population mean?

The width of a confidence interval
estimate for a population mean when the population standard
deviation is known will
(A) become narrower if the
size of the sample being used is increased and the confidence level
is unchanged.
(B) not change if
only the sample size is increased.
(C) become wider if
the sample size remains the same and the confidence level
decreases.
(D) become narrower if the
size of the sample is decreased and the confidence level is
unchanged....

Use the standard normal distribution or the t-distribution to
construct a
95%
confidence interval for the population mean. Justify your
decision. If neither distribution can be used, explain why.
Interpret the results. In a random sample of
fortyone
people, the mean body mass index (BMI) was
27.7
and the standard deviation was
6.24
Which distribution should be used to construct the confidence
interval? Choose the correct answer below.
(Use a t-distribution because the sample is random n>=30, and
o is...

Use the standard normal distribution or the t-distribution to
construct a 99% confidence interval for the population mean.
Justify your decision. If neither distribution can be used,
explain why. Interpret the results.
In a recent season, the population standard deviation of the
yards per carry for all running backs was 1.21. The yards per carry
of 25 randomly selected running backs are shown below. Assume the
yards per carry are normally distributed.
1.6 3.4 2.8 6.9 6.1 5.8 7.3 6.5...

The random sample shown below was selected from a normal
distribution.
5,5,3,10,10,3
a. Construct a 99% confidence interval for the population mean
mu. ( , ) (Round to two decimal places as needed.)
b. Assume that sample mean and sample standard deviation s
remain exactly the same as those you just calculated but that are
based on a sample of n = 25 observations. Repeat part a. What is
the effect of increasing the sample size on the width of...

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