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 12 concrete specimens from supplier A were tested for their compressive strength. The results gave an average of 85 MPa and a standard deviation of 4 MPa. From supplier B, 10 specimens were similarly tested and gave an average compressive strength of 81 MPa and a standard deviation of 5 MPa. (a) Using procedures of Hypothesis Testing, can we conclude at the 0.05 level of significance that the compressive strength of concrete from A exceeds that from B by more than 2 MPa? Assume the populations to be approximately normal with equal variances. (b) Is the assumption of equal variances in (a) justifiable at an a = 0.10?
At the alpha = 0.01 level , what is the correct conclusion for this test? The daily temperatures in fall and winter months in Virginia have a mean of 62F. A meteorologist in southwest Virginia believes the mean temperature is colder in this area. The meteorologist takes a random sample of 30 daily temperatures from the fall and winter months over the last five years in southwest Virginia. The mean temperature for the sample is 59 degrees * F with a standard deviation of 6.21 degrees * F The meteorologist conducts a one -sample t-test for and calculates a P value of 0.007. The meteorologist should reject the null hypothesis since 0.007 < 0.01 . There is convincing evidence that the mean temperature in fall and winter months in southwest Virginia is less than 62 F. The meteorologist should reject the null hypothesis since 0.007 < 0.01 . There is not convincing evidence that the mean temperature in fall and winter months in southwest Virginia is less than 62 F. The meteorologist…
Researchers measured the length of time people spend brushing their teeth. For the 154 subjects in their study, the mean was 72.8 seconds with a standard deviation of 23. 5 seconds. Use this information with a 0.10 significance level to test the claim that the mean teeth brushing time was less than 80 seconds. What is/are the critical value(s)? TTTArial 3 (12pt) v T- = - E - V · P 只igv
It has long been stated that the mean temperature of humans is 98.6 degrees F. However, two researchers currently involved in the subject thought that the mean temperature of humans is less than 98.6 degrees F. They measured the temperatures of 56 healthy adults 1 to 4 times daily for 3 days, obtaining 250 measurements. The sample data resulted in a sample mean of 98.3 degrees F and a sample standard deviation of 0.9 degrees F. Use the P-value approach to conduct a hypothesis test to judge whether the mean temperature of humans is less than 98.6 degrees F at the alpha equals0.01 level of significance.
The viscosity of a liquid detergent is supposed to average 800 centistokes at 25°C. A random sample of 16 batches of detergent is collected, and the average viscosity is 812. Suppose we know that the standard deviation of viscosity is σ = 25 centistokes. (a) What is the P-value for the test? (b) Find a 95 percent confidence interval on the mean.
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.
The nicotine content in cigarettes of a certain brand is normally distributed with mean (in milligrams) u and standard deviation o = 0.1. The brand advertises that the mean nicotine content of their cigarettes is 1.5 mg. Now, suppose a reporter wants to test whether the mean nicotine content is actually higher than advertised. He takes measurements from a SRS of 15 cigarettes of this brand. The sample yields an average of 1.6 mg of nicotine. Conduct a test using a significance level of a = 0.05. (a) The standardized test statistic (b) The critical value (endpoint of Rejection Region) is z* = (c) The final conclusion is OA. The nicotine content is probably higher than advertised. B. There is not sufficient evidence to show that the ad is misleading.
A sample of size 31 was gathered from high school seniors to estimate how many intended to attend the state university. It is known that the proportion of the population answering "yes" was 0.7. What are the mean and standard deviation, and standard error of the mean of this sample? mean = E(p) = %3D standard error = SD(p) (accurate to 3 decimal places)
Calcium is essential to tree growth. In 1990, the concentration of calcium in precipitation in a certain area was 0.11milligrams per liter (mg/L).A random sample of 10 precipitation dates in 2018 results in the following data table. Complete parts (a) through (c) below. (B) With 98% confidence, the mean concentration of calcium in precipitation in this area in 2018 is between
Solve using R commands and manually Suppose that blood chloride concentration (mmol/L) has a normal distribution with mean 104 andstandard deviation 5 (“Mathematical Model of Chloride Concentration in Human Blood,” J. of Med.Engr. and Tech., 2006: 25–30”).(a) What is the probability that chloride concentration equals, less than, and at most 104?(b) What is the probability that someone’s blood chloride concentration level is between 99 and 114?(c) What is the probability that someone’s blood chloride concentration level is above 120?
Vehicle speeds at a certain highway location are believed to have approximately a normal distribution with mean µ = 50 mph and standard deviation σ = 5 mph. The speeds for a randomly selected sample of n = 25 vehicles will be recorded. (a) Give numerical values for the mean and standard deviation of the sampling distribution of possible sample means for randomly selected samples of n = 25 from the population of vehicle speeds. Mean = s.d.(x) = (b) Use the Empirical Rule to find values that fill in the blanks in the following sentence. For a random sample of n = 25 vehicles, there is about a 95% chance that the mean vehicle speed in the sample will be between and mph. (c) Sample speeds for a random sample of 25 vehicles are measured at this location, and the sample mean is 59 mph. Given the answer to part (b), explain whether this result is consistent with the belief that the mean speed at this location is μ = 50 mph. A sample mean of 59 mph (when n = 25) --Select--- be consistent with…
The distribution of average wait times in drive-through restaurant lines in one town was approximately normal with mean �=185μ=185mu, equals, 185 seconds and standard deviation �=11σ=11sigma, equals, 11 seconds. A journalist wrote an article about the restaurants whose average drive-through wait times were in the top 25%25%25, percent for that town. What is the minimum average wait time for restaurants that the journalist included in the article?

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