Probability and Statistics for Engineering and the Sciences
9th Edition
ISBN: 9781305251809
Author: Jay L. Devore
Publisher: Cengage Learning
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Textbook Question
Chapter 7.1, Problem 6E
On the basis of extensive tests, the yield point of a particular type of mild steel-reinforcing bar is known to be
- a. Assuming this to be the case, if a sample of 25 modified bars resulted in a sample average yield point of 8439 lb, compute a 90% CI for the true average yield point of the modified bar.
- b. How would you modify the interval in part (a) to obtain a confidence level of 92%?
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To compare the dry braking distances from 30 to 0 miles per hour for two makes of automobiles, a safety engineer conducts braking tests for 35 models of Make A and 35 models of Make B. The mean braking distance for Make A is 44 feet. Assume the population standard deviation is 4.9 feet. The mean braking distance for Make B is 46 feet. Assume the population standard deviation is 4.7 feet. At α=0.10, can the engineer support the claim that the mean braking distances are different for the two makes of automobiles? Assume the samples are random and independent, and the populations are normally distributed. Complete parts (a) through (e).
To compare the dry braking distances from 30 to 0 miles per hour for two makes of automobiles, a safety engineer conducts braking tests for 35 models of Make A and 35 models of Make B. The mean braking distance for Make A is 43 feet. Assume the population standard deviation is 4.6 feet. The mean braking distance for Make B is 46 feet. Assume the population standard deviation is 4.5 feet. At α=0.10, can the engineer support the claim that the mean braking distances are different for the two makes of automobiles? Assume the samples are random and independent, and the populations are normally distributed.
The critical value(s) is/are
Find the standardized test statistic z for
μ1−μ2.
To compare the dry braking distances from 30 to 0 miles per hour for two makes of automobiles, a safety engineer conducts braking tests for 35 models of Make A and 35 models of Make B. The mean braking distance for Make A is
41 feet. Assume the population standard deviation is 4.6 feet.The mean braking distance for Make B is
42 feet. Assume the population standard deviation is 4.4 feet. At α=0.10, can the engineer support the claim that the mean braking distances are different for the two makes of automobiles? Assume the samples are random and independent, and the populations are normally distributed. Complete parts (a) through (e).
(a) Identify the claim and state Ho and Ha.
What is the claim?
A.The mean braking distance is different for the two makes of automobiles.
This is the correct answer.
B.The mean braking distance is the same for the two makes of automobiles.
C.The mean braking distance is less for Make A automobiles than Make B automobiles.
Your answer is…
Chapter 7 Solutions
Probability and Statistics for Engineering and the Sciences
Ch. 7.1 - Consider a normal population distribution with the...Ch. 7.1 - Each of the following is a confidence interval for...Ch. 7.1 - Suppose that a random sample of 50 bottles of a...Ch. 7.1 - A CI is desired for the true average stray-load...Ch. 7.1 - Assume that the helium porosity (in percentage) of...Ch. 7.1 - On the basis of extensive tests, the yield point...Ch. 7.1 - By how much must the sample size n be increased if...Ch. 7.1 - Let 1 0, 2 0, with 1 + 2 = . Then P(z1X-/nz2)=1-...Ch. 7.1 - a. Under the same conditions as those leading to...Ch. 7.1 - A random sample of n = 15 heat pumps of a certain...
Ch. 7.1 - Consider the next 1000 95% CIs for that a...Ch. 7.2 - The following observations are lifetimes (days)...Ch. 7.2 - The article Gas Cooking. Kitchen Ventilation, and...Ch. 7.2 - The negative effects of ambient air pollution on...Ch. 7.2 - Determine the confidence level for each of the...Ch. 7.2 - The alternating current (AC) breakdown voltage of...Ch. 7.2 - Exercise 1.13 gave a sample of ultimate tensile...Ch. 7.2 - The U.S. Army commissioned a study to assess how...Ch. 7.2 - The article Limited Yield Estimation for Visual...Ch. 7.2 - TV advertising agencies face increasing challenges...Ch. 7.2 - In a sample of 1000 randomly selected consumers...Ch. 7.2 - The technology underlying hip replacements has...Ch. 7.2 - The Pew Forum on Religion and Public Life reported...Ch. 7.2 - A sample of 56 research cotton samples resulted in...Ch. 7.2 - The Pew Forum on Religion and Public Life reported...Ch. 7.2 - The superintendent of a large school district,...Ch. 7.2 - Reconsider the CI (7.10) for p, and focus on a...Ch. 7.3 - Determine the values of the following quantities:...Ch. 7.3 - Determine the t critical value(s) that will...Ch. 7.3 - Determine the t critical value for a two-sided...Ch. 7.3 - Determine the t critical value for a lower or an...Ch. 7.3 - According to the article Fatigue Testing of...Ch. 7.3 - The article Measuring and Understanding the Aging...Ch. 7.3 - A sample of 14 joint specimens of a particular...Ch. 7.3 - Silicone implant augmentation rhinoplasty is used...Ch. 7.3 - A normal probability plot of the n = 26...Ch. 7.3 - A study of the ability of individuals to walk in a...Ch. 7.3 - Ultra high performance concrete (UHPC) is a...Ch. 7.3 - Exercise 72 of Chapter 1 gave the following...Ch. 7.3 - Prob. 40ECh. 7.3 - A more extensive tabulation of t critical values...Ch. 7.4 - Determine the values of the following quantities:...Ch. 7.4 - Determine the following: a. The 95th percentile of...Ch. 7.4 - The amount of lateral expansion (mils) was...Ch. 7.4 - Wire electrical-discharge machining (WEDM) is a...Ch. 7.4 - Wire electrical-discharge machining (WEDM) is a...Ch. 7 - Example 1.11 introduced the accompanying...Ch. 7 - The article Distributions of Compressive Strength...Ch. 7 - For those of you who dont already know, dragon...Ch. 7 - A journal article reports that a sample of size 5...Ch. 7 - Unexplained respiratory symptoms reported by...Ch. 7 - High concentration of the toxic element arsenic is...Ch. 7 - Aphid infestation of fruit trees can be controlled...Ch. 7 - It is important that face masks used by...Ch. 7 - A manufacturer of college textbooks is interested...Ch. 7 - The accompanying data on crack initiation depth...Ch. 7 - In Example 6.8, we introduced the concept of a...Ch. 7 - Prob. 58SECh. 7 - Prob. 59SECh. 7 - Prob. 60SECh. 7 - Prob. 61SECh. 7 - Prob. 62SE
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- A person's body mass index (BMI) is computed by dividing the weight (kg) by the square of height (m). The accompanying table contains the BMI statistics for random samples of males and females. Assume that the two samples are independent simple random samples selected from normally distributedpopulations, and do not assume that the population standard deviations are equal. Let population 1 be females. Female BMI: n=69 x=29.14 s=7.41 Male BMI: n=79 x=28.18 s=5.24 The test statistic is The P-value is Construct a confidence interval appropriate for testing the claim in part (a). The ___% confidence interval estimate is ___<μ1−μ2<___.arrow_forwardThe strength of concrete depends, to some extent, on the method used for drying. Two different drying methods showed the following results for independently tested specimens (measurements in psi): Do the methods appear to produce concrete with different mean strengths? Use α = 0.05 .arrow_forwardA manufacturing company produces bearings. One line of bearings is specified to be 1.64 centimeters (cm) in diameter. A major customer requires that the variance of the bearings be no more than .001 cm². The producer is required to test the bearings before they are shipped, and so the diameters of 16 bearings are measured with a precise instrument, resulting in the following values. Assume bearing diameters are normally distributed. Use the data and a = 0.01 to test to determine whether the population of these bearings is to be rejected because of too high a variance. 1.68 1.62 1.63 1.70 1.66 1.63 1.65 1.71 1.64 1.69 1.57 1.64 1.59 1.66 1.63 1.65 Appendix A Statistical Tables (Round your answer to 2 decimal places, e.g. 15.25.) The value of the test statistic is and we reject the null hypothesis ⇒arrow_forward
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