An industrial engineer is analyzing the structural strength of a concrete aggregate. Structural strengthis normally distributed with o2 = 1000 (psi)². A random sample of 12 specimens has a mean strengthof x = 3250 psi. Compare the width of the 95% confidence interval with the width of 99% confidenceinterval. Which has higher precision of estimation on the unknown µ? Includeyoursolutions.

Confidence interval : The likelihood that a parameter can fall between 2 values round the mean is…

Answered: An industrial engineer is analyzing the…

MATLAB: An Introduction with Applications

6th Edition

ISBN:9781119256830

Author:Amos Gilat

Publisher:Amos Gilat

Chapter1: Starting With Matlab

Section: Chapter Questions

Problem 1P

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The concentration of carbon monoxide (CO) in a gas sample is measured by a spectrophotometer and found to be 85 ppm. Through long experience with this instrument, it is believed that its measurements are unbiased and normally distributed, with an uncertainty (standard deviation) of 8 ppm. Find a 95% confidence interval for the concentration of CO in this sample.
A company that produces white bread is concerned about the amount of sodium in its bread. The company takes a simple random sample of 100 slices of bread and computes the sample mean to be 103 milligrams of sodium per slice with a standard deviation of 10 milligrams. Construct a 99% confidence interval for the unknown mean sodium level.
A random sample of 50 roundtrip flights between New York and Chicago has an average airfare of $400 with a sample standard deviation of $50.0. The critical value for an 95% confidence interval around this sample mean is ________.
A factory produces steel sheets whose weights are known to be normallydistributed with a standard deviation of 1.7kg. A random sample of 47 sheetshad a mean weight of 27.3kg. Construct a 95% confidence interval for thepopulation mean.
To study the effect of curing temperature on shear strength of a certain rubber compound, 80 specimens were cured at 150°C and 95 were cured at 130°C. The specimens cured at 150°C had an average shear strength of 620 psi, with a standard deviation of 20 psi. Those cured at 130°C had an average shear strength of 750 psi, with a standard deviation of 30 psi. Find a 95% confidence interval for the difference between the mean shear strengths of specimens cured at the two temperatures.
A thread manufacturer tests a sample of 36 lengths of a certain type of thread made of blended materials from a production run of a total of 260 and obtains a mean tensile strength of 9.34 lbs. The population standard deviation for the 260 items has always been .04 Ib. a. Assuming tensile strengths are normally distributed, construct a 95% confidence interval for the mean tensile strength of this thread.
In a sample of n=19 lichen specimens, the researchers found the mean and standard deviation of the amount of the radioactive element, cesium-137, that was present to be 0.009 and 0.006 microcurie per milliliter, respectively. Suppose the researchers want to increase the sample size in order to estimate the mean μ to within 0.002 microcurie per milliliter of its true value, using a 95% confidence interval.
While performing a strenuous task, the pulse rate of 25 workers increased on the average by 18.4 beats per minute with a standard deviation of 4.9 beats per minute. Use the 0.05 level of significance to test the null hypothesis that = 30.0 for such increases in the pulse rate (while performing the given task) against the alternative hypothesis that < 30.0. Also construct a 95% confidence interval for the corresponding population standard deviation.
The diameter of holes for a cable harness is known to have a normal distribution with a standard deviation of 0.01 inches. A random sample of size 10 yields an average diameter of 1.5045 inches. Find the 99% and 95% two-tailed/two-sided confidence intervals on the mean diameter and explain the difference of the interval between the two confidence levels.
The bottlers of the new soft drink “Guzzle” are experiencing problems with the filling mechanism for their 16 floz bottles. To estimate the standard deviation of the fill volume, the filled volume for 20 bottles was measured, yielding a sample standard deviation of 0.1 floz. Compute a 95% confidence interval for the standard deviation σ.
During a natural gas shortage, a gas company randomly sampled residential gas meters in order to monitor daily gas consumption. On a particular day, a sample of 100 meters showed a sample mean of 250 cubic feet and a sample standard deviation of 50 cubic feet. Provide a 90% confidence interval estimate of the mean gas consumption for the population.
A random sample of 20 acres gave a mean yield of sugarcane equal to 41.2 tons per acre with astandard deviation of 3 tons. Assuming that the yield of sugarcane per acre is normallydistributed,a. Construct a 90% confidence interval for the population mean.b. What is the margin of error for this estimate in part a?

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