6. A civil engineer is analyzing the compressive strength of concrete. Compressive strength isnormally distributed with o? = 1000(psi)². A random sample of 12 specimens has a meancompressive strength of x = 3250 psi.(a) Construct a 95% two-sided confidence interval on mean compressive strength.(b) Construct a 99% two-sided confidence interval on mean compressive strength.(c) Compare the width of this confidence interval with the width of the one found in part (a).

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Answered: 6. A civil engineer is analyzing the…

A First Course in Probability (10th Edition)

10th Edition

ISBN:9780134753119

Author:Sheldon Ross

Publisher:Sheldon Ross

Chapter1: Combinatorial Analysis

Section: Chapter Questions

Problem 1.1P: a. How many different 7-place license plates are possible if the first 2 places are for letters and...

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A sample of 50 lenses used in eyeglasses yields a sample mean thickness of 3.07 mm and a sample standard deviation of 0.36 mm. The desired true average thickness of such lenses is 3.20 mm. Does the data strongly suggest that the true average thickness of such lenses is something other than what is desired? Test using alpha of 0.05. what is the result of the test
We want to estimate the number of pounds of ground beef produced during a month. The firm processes 25,000 cows every year in this plant, and samples 500 cows for this investigation. This sample produced i = 290 lbs ground of beef per cow with a sample standard deviation of s = 40 lbs. The plant is paid S.75/b for the beef. a) Find a 90% confidence interval for ground beef. The plant manager bragged about the productivity of his workers and gave them a bonus because he says they slaughtered 2,500 cows and made $560,000 for the plant this month. Should the board of directors investigate? Why or why not? b) Type here to search 8. 9. E R T Y D F G K L ent pause V B M alt ctri
erproduction of uric acid in the body can be an Indication of cell breakdown. This may be an advance indication of illness such as go adult male patlent has taken eleven blood tests for uric acid. The mean concentration was x = 5.30 mg/dl. The distribution of uric rmal, with o = 1.95 mg/dI. a) Find a 95% confidence interval for the population mean concentration of uric acid in this patient's blood. What is the margin of ei lower limit upper limit margin of error (b) What conditions are necessary for your calculations? (Select all that apply.) normal distribution of uric acid uniform distribution of uric acid o is known On is large Oo is unknown (c) Interpret your results in the context of this problem. O The probability that this interval contains the true average uric acid level for this patient is 0.95. O We are 5% confident that the true uric acid level for this patient falls within this interval. O We are 95% confident that the true uric acid level for this patient falls within…
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The EPA reports that the exhaust emissions for a certain car model has a normal distribution with a mean of 1.45 grams of nitrous oxide per mile and a standard deviation of 0.4. The car manufacturer claims their new process reduces the mean level of exhaust emitted for this car model. A SRS of 28 cars is taken and the mean level of exhaust emitted for this sample is 1.21 grams. (a) Calculate the p-value (b)What is the decision at the 0.01 significance level?
The owner of a coin-operated hot coffee machine has received claims that there is an error in his machine, and it is not dispensing enough hot coffee into hand-held cups. He takes a random sample of 46 “8 oz servings” from a large number of servings and finds that the mean is 7.93 fluid ounces with a standard deviation of 0.38 ounces. Is this evidence of error in the machine if ? = 0.05? Use the P-Value method.
An SRS of 400 high school seniors gained an average of x = 21.87 points in their second attempt at the SAT Mathematics exam. Assume that the change in score has a Normal distribution with standard deviation o = 48.66. We want to estimate the mean change in score µ in the population of all high school seniors. (a) Using the 68-95-99.7 Rule or the z-table (Table A), give a 95% confidence interval (a, b) for u based on this sample. (Enter your answers rounded to three decimal places. If you are using CrunchIt, adjust the default precision under Preferences as necessary. See the instructional video on how to adjust precision settings.) a: b: (b) Based on your confidence interval in part (a), how certain are you that the mean change in score u in the population of all high school seniors is greater than 0? O The upper endpoint of the interval is larger than 0, so we are 95% certain that the mean change in score in the population of all high school seniors is greater than 0. O We cannot be…
The level of calciumin the blood of healthy young adults follows aNormal distributionwithmean μ = 10milligrams per deciliter and standard deviation = 0.4. A clinicmeasures theblood calcium of 100 healthy pregnant young women at their first visit for prenatal care.The mean of these 100 measurements is ¯ x = 9.8. Is this evidence that the mean calciumlevel in the population of healthy pregnant young women is less than 10? To answer this,test the hypotheses H0 : μ = 10 versus Ha : μ < 10 at the 5% significance level.(a) What is the value of the P-value?(b) Determine which of the following statements is true.• H0 should be rejected.• H0 should not be rejected.• Ha should be rejected.• There is a 5% chance that the null hypothesis is true.
ou intend to estimate a population mean with a confidence interval. You believe the population to have a normal distribution. Your sample size is 6.a.) The degrees of freedom df=df=b.) Use the t-table on page 4 to find the critical value tctc that corresponds to a confidence level of 95%.tc=(Use 4 decimal places)
According to recent information from the Speedo Automobile Association, the mean age of passenger cars in USA is 8.4 years. A sample of 36 cars in the student’s lot at College X showed the mean age to be 9.0 years. The standard deviation of this sample was 2.8 years. At the 0.01 significance level can we conclude that the mean age for these cars of College X students is more than 8.4 years? Let the critical value of this test statistic be 2.575 (Z-table value). a) State the null hypothesis and the alternative hypothesis for this test. b) Compute the value of the test statistic. c) What is your decision regarding the null hypothesis? Interpret your decision.
The level of lead in the blood was determined for a sample of 152 male hazardous-waste workers age 20-30 and also for a sample of 86 female workers, resulting in a mean + standard error of 5.3 ± 0.3 for the men and 3.6 t 0.2 for the women. Calculate an estimate of the difference between true average blood lead levels for male and female workers in a way that provides information about reliability and precision. (Use a 95% confidence interval. Round your answers to two decimal places.) Interpret the interval. O we are 95% confident that the true average blood lead level for male workers is less than that of female workers by an amount within the confidence interval. O we are 95% confident that the true average blood lead level for male workers is greater than that of female workers by an amount outside the confidence interval. O we cannot draw a conclusion from the given information. O we are 95% confident that the true average blood lead level for male workers is greater than that of…
A warehouse owner wants to know the average weight of books at his facility. He weighs 18 books and finds that the sample has a mean weight of 9.41 pounds and standard deviation of 2.89 pounds. Construct a 99%confidence interval for the population mean of book weights. Assume the population is normally distributed.Choose the correct confidence interval and critical value used in the calculation. (7.46,11.36)(tc=2.8609) (7.83,10.99)(Zc=2.326) (7.44,11.38) (tc=2.8982) (7.45,11.37) (tc=2.8784) (7.66,11.16)(Zc=2.576)

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