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20 Practice Questions if anyone can help Practice Set 4 1. Find z for each of the following confidence levels. Round to two decimal places. 90% 95% 96% 97% 98% 99% 2. For a data set obtained from a random sample, n = 81 and x = 48.25. It is known that σ = 4.8. What is the point estimate of μ? Round to two decimal places Make a 95% confidence interval for μ. What is the lower limit? Round to two decimal places. Make a 95% confidence interval for μ. What is the upper limit? Round to two decimal places. What is the margin of error of estimate for part b? Round to two decimal places. 3. Determine the sample size (nfor the estimate of μ for the following. E = 2.3, σ = 15.40, confidence level = 99%. Round to the nearest whole number. E = 4.1, σ = 23.45, confidence level = 95%. Round to the nearest whole number. E = 25.9, σ = 122.25, confidence level = 90%. Round to the nearest whole number. 4. True or False. a.The null hypothesis is a claim about a population parameter that is assumed to be false until it is declared false.
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Practice Set 3
QNT/275 Version 6
University of Phoenix Material
Practice Set 3
Practice Set 3
1. Let x be a continuous random variable. What is the probability that x assumes a single value, such as
a (use numerical value)?
2. The following are the three main characteristics of a normal distribution.
A. The total area under a normal curve equals _____.
B. A normal curve is ___________ about the mean. Consequently, 50% of the total area
under a normal distribution curve lies on the left side of the mean, and 50% lies on the
right side of the mean.
C. Fill in the blank. The tails of a normal distribution curve extend indefinitely in both
directions without touching or crossing the horizontal axis. Although a normal curve
never meets the ________ axis, beyond the points represented by µ – 3σ to µ + 3σ
it becomes so close to this axis that the area under the curve beyond these points in
both directions is very close to zero.
3. For the standard normal distribution, find the area within one standard deviation of the
mean that is, the area between μ − σ and μ + σ. Round to four decimal places.
4. Find the area under the standard normal curve. Round to four decimal places.
a)
b)
c)
d)
e)
between z = 0 and z = 1.95
between z = 0 and z = −2.05
between z = 1.15 and z = 2.37
from z = −1.53 to z = −2.88
from z = −1.67 to z = 2.24
5. The probability distribution of the population data is called the (1) ________. Table 7.2 in the text
provides an example of it. The probability distribution of a sample statistic is called its (2)
_________. Table 7.5 in the text provides an example it.
A.
B.
C.
D.
Probability distribution
Population distribution
Normal distribution
Sampling distribution
6. ___________ is the difference between the value of the sample statistic and the value of the
corresponding population parameter, assuming that the sample is random and no non-sampling
error has been made. Example 7–1 in the text displays sampling error. Sampling error occurs
only in sample surveys.
7. Consider the following population of 10 numbers. 20 25 13 19 9 15 11 7 17 30
a) Find the population mean. Round to two decimal places.
Copyright © 2017 by University of Phoenix. All rights reserved.
1
Practice Set 3
QNT/275 Version 6
2
b) Rich selected one sample of nine numbers from this population. The sample included the
numbers 20, 25, 13, 9, 15, 11, 7, 17, and 30. Calculate sampling error for this sample. Round to
decimal places.
8. Fill in the blank. The F distribution is ________ and skewed to the right. The F distribution has two
numbers of degrees of freedom: df for the numerator and df for the denominator. The units of an F
distribution, denoted by F, are nonnegative.
9. Find the critical value of F for the following. Round to two decimal places.
a) df = (3, 3) and area in the right tail = .05
b) df = (3, 10) and area in the right tail = .05
c) df = (3, 30) and area in the right tail = .05
10. The following ANOVA table, based on information obtained for three samples selected from three
independent populations that are normally distributed with equal variances, has a few missing values.
Source of
Variation
Between
Within
Total
Degrees of
Freedom
2
1)
Sum of
Squares
2)
89.3677
12
4)
Mean
Square
19.2813
3)
Value of the
Test Statistic
F = ___5)__ = 7)
6)
Refer to Chapter 12, Example 12-2 and Tables 12.3 & 12.4, page 490.
a) Find the missing values 1) – 7) and complete the ANOVA table. Round to four decimal places.
b) Using α = .01, what is your conclusion for the test with the null hypothesis that the means of the
three populations are all equal against the alternative hypothesis that the means of the three
populations are not all equal? Select from following:
i.
ii.
iii.
iv.
Reject H0. Conclude that the means of the three populations are equal.
Reject H0. Conclude that the means of the three populations are not equal.
Do not reject H0. Conclude that the means of the three populations are equal.
Do not reject H0. Conclude that the means are of the three populations are not equal.
Copyright © 2017 by University of Phoenix. All rights reserved.
Practice Set 4
QNT/275 Version 6
University of Phoenix Material
Practice Set 4
Practice Set 4
1. Find z for each of the following confidence levels. Round to two decimal places.
A. 90%
B. 95%
C. 96%
D. 97%
E. 98%
F. 99%
2. For a data set obtained from a random sample, n = 81 and x = 48.25. It is known
that σ = 4.8.
A. What is the point estimate of μ? Round to two decimal places
B. Make a 95% confidence interval for μ. What is the lower limit? Round to two decimal
places.
C. Make a 95% confidence interval for μ. What is the upper limit? Round to two decimal
places.
D. What is the margin of error of estimate for part b? Round to two decimal places.
3. Determine the sample size (nfor the estimate of μ for the following.
A. E = 2.3, σ = 15.40, confidence level = 99%. Round to the nearest whole number.
B. E = 4.1, σ = 23.45, confidence level = 95%. Round to the nearest whole number.
C. E = 25.9, σ = 122.25, confidence level = 90%. Round to the nearest whole number.
4. True or False.
a.The null hypothesis is a claim about a population parameter that is assumed to be false until
it is declared false.
A. True
B. False
b. An alternative hypothesis is a claim about a population parameter that will be true if the
null hypothesis is false.
A. True
B. False
c. The critical point(s) divide(s) is some of the area under a distribution curve into rejection
and nonrejection regions.
A. True
B. False
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Practice Set 4
QNT/275 Version 6
d. The significance level, denoted by α, is the probability of making a Type II error, that is,
the probability of rejecting the null hypothesis when it is actually true.
A. True
B. False
e. The nonrejection region is the area to the right or left of the critical point where the null
hypothesis is not rejected.
A. True
B. False
5. A Type I error is committed when
A. A null hypothesis is not rejected when it is actually false
B. A null hypothesis is rejected when it is actually true
C. An alternative hypothesis is rejected when it is actually true
6. Consider H0: μ = 45 versus H1: μ < 45. A random sample of 25 observations produced a sample mean of 41.8. Using α = .025 and the population is known to be normally distributed with σ = 6. A. What is the value of z? Round to two decimal places. B. Would you reject the null hypothesis? 1. Reject Ho 2. Do not reject Ho 7. The following information is obtained from two independent samples selected from two normally distributed populations. n1 = 18 x1 = 7.82 σ1 = 2.35 n2 =15 x2 =5.99 σ2 =3.17 A. What is the point estimate of μ1 − μ2? Round to two decimal places. B. Construct a 99% confidence interval for μ1 − μ2. Find the margin of error for this estimate. Round to two decimal places. 8. The following information is obtained from two independent samples selected from two populations. n1 =650 x1 =1.05 σ1 =5.22 n2 =675 x2 =1.54 σ2 =6.80 Test at a 5% significance level if μ1 is less than μ2. a) Identify the appropriate distribution to use. Copyright © 2017 by University of Phoenix. All rights reserved. 2 Practice Set 4 QNT/275 Version 6 A. t distribution B. normal distribution b) What is the conclusion about the hypothesis? A. Reject Ho B. Do not reject Ho 9. Using data from the U.S. Census Bureau and other sources, www.nerdwallet.com estimated that considering only the households with credit card debts, the average credit card debt for U.S. house- holds was \$15,523 in 2014 and \$15,242 in 2013. Suppose that these estimates were based on random samples of 600 households with credit card debts in 2014 and 700 households with credit card debts in 2013. Suppose that the sample standard deviations for these two samples were \$3870 and \$3764, respectively. Assume that the standard deviations for the two populations are unknown but equal. a) Let μ1 and μ2 be the average credit card debts for all such households for the years 2014 and 2013, respectively. What is the point estimate of μ1 − μ2? Round to two decimal places. Do not include the dollar sign. b) Construct a 98% confidence interval for μ1 − μ2. Round to two decimal places. Do not include the dollar sign. 1. What is the lower bound? Round to two decimal places. 2. What is the upper bound? Round to two decimal places. c) Using a 1% significance level, can you conclude that the average credit card debt for such households was higher in 2014 than in 2013? Use both the p-value and the critical-value approaches to make this test. A. Reject Ho B. Do not reject Ho 10. Gamma Corporation is considering the installation of governors on cars driven by its sales staff. These devices would limit the car speeds to a preset level, which is expected to improve fuel economy. The company is planning to test several cars for fuel consumption without governors for 1 week. Then governors would be installed in the same cars, and fuel consumption will be monitored for another week. Gamma Corporation wants to estimate the mean difference in fuel consumption with a margin of error of estimate of 2 mpg with a 90% confidence level. Assume that the differences in fuel consumption are normally distributed and that previous studies suggest that an estimate of sd=3sd=3 mpg is reasonable. How many cars should be tested? (Note that the critical value of tt will depend on nn, so it will be necessary to use trial and error.) Copyright © 2017 by University of Phoenix. All rights reserved. 3 ... Purchase answer to see full attachment

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