9. Measurements of the diameters of a random sample of 13 ball bearings made by machine X during one week showed a mean of 8.22 mm and a standard deviation of 0.38 mm. However, other measurements of the diameters ofa random sample of 11 ball bearings made by machine Y during the same week showed a mean of 7.68 mm and a standard deviation of 0.42 mm. Assuming the diameters are normally distributed with equal variance, a) Construct a 99% confidence interval for the difference in the true mean diameters of ball bearings made by the two machines. b) Based on your answer in part (a), are you 99% confident that the true mean diameters of ball bearings made by machines X and Y are not equal? Justify your answer.

9. Measurements of the diameters of a random sample of 13 ball bearings made by machine X during one week showed a mean of 8.22 mm and a standard deviation of 0.38 mm. However, other measurements of the diameters ofa random sample of 11 ball bearings made by machine Y during the same week showed a mean of 7.68 mm and a standard deviation of 0.42 mm. Assuming the diameters are normally distributed with equal variance, a) Construct a 99% confidence interval for the difference in the true mean diameters of ball bearings made by the two machines. b) Based on your answer in part (a), are you 99% confident that the true mean diameters of ball bearings made by machines X and Y are not equal? Justify your answer.

MATLAB: An Introduction with Applications

6th Edition

ISBN:9781119256830

Author:Amos Gilat

Publisher:Amos Gilat

Chapter1: Starting With Matlab

Section: Chapter Questions

Problem 1P

See similar textbooks

Similar questions

Suppose that for a random sample of 250 firms that revalued their fixed assets, the mean ratio of debt to tangible assets was 0.629, and the sample standard deviation was 0.177. For an independent random sample of 450 firms that did not revalue their fixed assets, the mean ratio of debt to tangible assets was 0.599, and the sample standard deviation was 0.163. Assuming that the population distributions are normal with equal variances, find a 95% confidence interval for the difference between the two population means. E Click the icon to view a table of upper critical values of Student's t distribution. A 95% confidence interval for the difference between the two population means is (Round to four decimal places as needed.)
4. It is known that the average weight of babies born in a maternity ward is 3.2 kg and the variance of 0.09 kg 2corresponds to the normal distribution. According to this; a) Assuming that an average of 200 babies are born a day, how many of these babies weigh more than 4 kg? b) What weight is the lightest 5% lighter than babies?
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 1% level of significance) that there is no difference between the average yields using the different fertilizers, what is the null and alternative hypotheses?
A motorcar industry research study found that the tyre lifespan for economic sedan cars is normally distributed with a mean of 30 000km and a standard deviation of 4 500km. If a random sample of 100 vehicles is selected, calculate the standard error of the sample means
In drilling a vertical wellbore, the spacing between major fractures are recorded It has been found that this spacing is having a mean of 1800 ft and a variance of 3,240,000 ft2. In the first 2000 ft drilling, there was no present of major fracture in the well. Determine the probability that there is a major fracture at the depth of 2000-3500 ft.
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?
0) A coin-operated drink machine was designed to discharge a mean of 7 fluid ounces of coffee per cup. In a test of the machine, the discharge amounts in 18 randomly chosen cups of coffee from the machine were recorded. The sample mean and sample standard deviation were 7.19 fluid ounces and 0.28 fluid ounces, respectively. If we assume that the discharge amounts are approximately normally distributed, there enough evidence, to conclude that the population mean discharge, µ, differs from 7 fluid ounces? Use the 0.05level of significance
Steel rods manufactured in a plant must be a minimum of 2 metres in length in order to pass through an inspection procedure. Steel rods with lengths that are normally distributed, with a mean of 2.1 metres and a standard deviation of 0.1 metres, are produced during the manufacturing process. A random sample of 25 steel rods is chosen, and their lengths are measured using a tape measure. i. Decide on the appropriate distribution of the sample mean of the 25 steel rods in the sample using the appropriate distribution formula. ii. Calculate the probability that the sample mean of steel rods that meet the minimum length requirement is the same as the mean of the entire sample. iii. For example, if the observed sample mean length of steel rods is 2.15, calculate the 98% two-sided confidence interval for the true mean length of the manufacturing process, assuming that it is not known.
The University of Florida is interested in determining if there is a difference in the amount of money spent on food every two weeks between male and female students. They take a random sample of 20 male students (group 2) and 20 female students (group 1). They also find that xbar2 is 106 with a standard deviation of 14, and xbar1 is 146 with a standard deviation of 39. Do not assume equal variances. Find the test statistic for the difference in the amount of money spent. (Round your answer to one number after the decimal.)
The heights of men in a certain city are normally distributed with a mean of 275 cm and a variance of 25cm. Compute the minimum height for the top sixteen percent of the men in the city.
A company produces steel rods. The lengths of the steel rods are normally distributed with a mean of 159.9 cm and a standard deviation of 2.1 cm. For shipment, 28 steel rods are bundled together. Note: Even though our sample size is less than 30, we can use the z score because1) The population is normally distributed and2) We know the population standard deviation, sigma. Find the probability that the average length of a randomly selected bundle of steel rods is between 159.4 cm and 160.4 cm.Enter your answer as a number accurate to 4 decimal places.
In the manufacture of steel rollers to fit an assembly, the external diameter is considered to be a random variable with mean equal to 23 mm and variance equal to 0.0036 cm2. 1.5 is supported standard deviations more than the mean and 3.5 standard deviations below average. A piece with a diameter below such specifications is considered waste, whereas a piece with a diameter larger than specified must be reprocessed. Which is the percentage of pieces that:to. They are being wasted.b. They need to be reprocessed.c. Acceptable.d. If you want to establish that the reprocessing is 5% of the rollers and waste of 1%, than specification limit would recommend.