An experiment was performed to compare the abrasive wear of twodifferent coating materials on the cutting tools:• Coating material A: 11 pieces were tested, which gave average wear of 85 units with asample standard deviation of 4 units.• Coating material B: 10 pieces were tested, which gave average wear of 81 units with asample standard deviation of 5 units.Assume the populations to be normal.1) Can we conclude at the 0.05 level of significance that the population variances of material Aand material B are different?2) Can we conclude at the 0.05 level of significance that the abrasive wear of material A exceedsthat of material B if the population variances of material A and B are equal?

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Answered: An experiment was performed to compare…

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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1) Sampling Distribution for Sample Variances a) A cell phone manufacturer wants to advertise their new extended-life batteries. They believe the lifetimes are normally distributed with o = 1.15 hr. A test engineer takes a sample of 10 batteries and calculates a sample standard deviation of 1.3 hr. Can the manufacturer confidently advertise the standard deviation in the lifetime of their new batteries? Use critical values of X1.95 and X3.05 (a 90% window). i) Find the value of the test statistic for this sample and the two critical values. ii) 2 X0.95 = YES x² = Can the manufacturer confidently advertise the standard deviation in the lifetime of their new batteries? Circle YES or NO and briefly explain your answer. NO X0.05 =
An agricultural company is trying to decide which type of fertilizer to use on its crops. The company concerned with the average yield on its crops as well as the variance of their yields. In a sample of 41 different fields with using fertilizer A, the average crop yield per acre is 185 tons with a standard deviation of 35 tons. In a separate sample of 61 different fields using fertilizer B, the average crop yield is 175 tons with a standard deviation of 28 tons. When testing the hypothesis (at the 5% level of significance) that the variance of one of these yields is significantly larger than the other, what is the null and alternative hypotheses?
An avionics company uses a new production method to manufacture aircraft altimeters. A single random sample of new altimeters resulted in the errors listed below. Use a 5% significance level to test the claim that the new production method has errors with a standard deviation greater than 32.2 ft, which was the standard deviation for the old production model (o). If it appears that the standard deviation is greater, does the new production method appear to be better or worse than the old method? Should the company take any action? -42 78 -22 -72 -45 15 17 51 -5 -53 -9 -109 Find the upper and lower boundaries of the 95% confidence interval for o. 98 37 32 73 89
It is known that the zinc concentrations are usually normally distributed and havea variance of 0.09 grams per milliliter squared. In a study, the average zinc concentrationsrecovered from a random sample of zinc measurements in 22 different locations was found tobe 2.6 grams per milliliter. Calculate and interpret a 90% confidence interval for the overallaverage zinc concentration.
The void volume within a textile fabric affects comfort, flammability, and insulation properties. Permeability of a fabric refers to the accessibility of void space to the flow of a gas or liquid. An article gave summary information on air permeability (cm3/cm2/sec) for a number of different fabric types. Consider the following data on two different types of plain-weave fabric: Fabric Type Sample Size Sample Mean Sample Standard Deviation Cotton 10 51.41 0.75 Triacetate 10 132.15 3.59 Assuming that the porosity distributions for both types of fabric are normal, let's calculate a confidence interval for the difference between true average porosity for the cotton fabric and that for the acetate fabric, using a 95% confidence level. Before the appropriate t critical value can be selected, df must be determined: df = 0.5625 10 + 12.8881 10 2 (0.5625/10)2 9 + (12.8881/10)2 9 = 1.8092 0.1849…
Example 2 : A drilling machine bores holes with a mean diameter of 0.5230 cm and a standard deviation of 0.0032 cm. Calculate the 2 - sigma and 3 - sigma upper and lower control limits for means of samples 4, and prepare a control chart.
On the basis of data provided by a Romac Salary survey, the variance in annual salaries for seniors in public accounting firms is approximately 2.1 and the variance in annual salaries for managers in public accounting firms is approximately 11.1. The salary data were provided in thousands of dollars. Assuming that the salary data were based on samples of 25 seniors and 26 managers, test the hypothesis that the population variances in the salaries are equal. At a 0.05 level f significance, what is your conclusion? use excel please
In a study of microplastics in our environment, it was determined that there are 5.25 trillion plastic pieces floating in the ocean, weighing more than 250,000 tons. In a recent expedition to examine whether increases in plastic production have led to changes in ocean microplastics, 16 samples were taken at various locations in the Pacific Ocean. It was determined that the average concentration was 9.5 particles per liter of ocean water with a sample standard deviation of 6. In one of the earliest research expeditions to study microplastics in the ocean conducted in 2009, it was determined that the average concentration of microplastics was 6 particles per liter (consider this the population or reference mean). What is the critical value for the two-tailed alternative hypothesis at alpha = 5%? (Hint: This is the value in the table that you will compare your test statistic to in order to determine the outcome of the hypothesis test). 2.131 1.746 2.120 1.753

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