The derailment of a freight train due to the catastrophic failure of a traction motor armature bearing provided the impetus for a study reported in the article “Locomotive Traction Motor Armature Bearing Life Study” ( Lubrication Engr ., Aug. 1997: 12–19) . A sample of 17 high-mileage traction motors was selected, and the amount of cone penetration (mm/10) was determined both for the pinion bearing and for the commutator armature bearing, resulting in the following data: Motor 1 2 3 4 5 6 Commutator 211 273 305 258 270 209 Pinion 226 278 259 244 273 236 Motor 7 8 9 10 11 12 Commutator 223 288 296 233 262 291 Pinion 290 287 315 242 288 242 Motor 13 14 15 16 17 Commutator 278 275 210 272 264 Pinion 278 208 281 274 268 Calculate an estimate of the population mean difference between penetration for the commutator armature bearing and penetration for the pinion bearing, and do so in a way that conveys information about the reliability and precision of the estimate. [ Note: A normal probability plot validates the necessary normality assumption.] Would you say that the population mean difference has been precisely estimated? Does it look as though population mean penetration differs for the two types of bearings? Explain.

BuyFind

Probability and Statistics for Eng...

9th Edition
Jay L. Devore
Publisher: Cengage Learning
ISBN: 9781305251809
BuyFind

Probability and Statistics for Eng...

9th Edition
Jay L. Devore
Publisher: Cengage Learning
ISBN: 9781305251809

Solutions

Chapter 9, Problem 74SE
Textbook Problem

The derailment of a freight train due to the catastrophic failure of a traction motor armature bearing provided the impetus for a study reported in the article “Locomotive Traction Motor Armature Bearing Life Study” (Lubrication Engr., Aug. 1997: 12–19). A sample of 17 high-mileage traction motors was selected, and the amount of cone penetration (mm/10) was determined both for the pinion bearing and for the commutator armature bearing, resulting in the following data:

Motor
1 2 3 4 5 6
Commutator 211 273 305 258 270 209
Pinion 226 278 259 244 273 236
Motor
7 8 9 10 11 12
Commutator 223 288 296 233 262 291
Pinion 290 287 315 242 288 242
Motor
13 14 15 16 17
Commutator 278 275 210 272 264
Pinion 278 208 281 274 268

 Calculate an estimate of the population mean difference between penetration for the commutator armature bearing and penetration for the pinion bearing, and do so in a way that conveys information about the reliability and precision of the estimate. [Note: A normal probability plot validates the necessary normality assumption.] Would you say that the population mean difference has been precisely estimated? Does it look as though population mean penetration differs for the two types of bearings? Explain.

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Chapter 9 Solutions

Probability and Statistics for Engineering and the Sciences
Ch. 9.1 - The level of lead in the blood was determined for...Ch. 9.1 - The accompanying summary data on total cholesterol...Ch. 9.1 - A mechanical engineer wishes to compare strength...Ch. 9.1 - The level of monoamine oxidase (MAO) activity in...Ch. 9.1 - a. Show for the upper-tailed test with 1 and 2...Ch. 9.1 - To decide whether two different types of steel...Ch. 9.2 - Determine the number of degrees of freedom for the...Ch. 9.2 - Which way of dispensing champagne, the traditional...Ch. 9.2 - Suppose 1 and 2 are true mean stopping distances...Ch. 9.2 - Use the data of Exercise 19 to calculate a 95% CI...Ch. 9.2 - Quantitative noninvasive techniques are needed for...Ch. 9.2 - According to the article Modeling and Predicting...Ch. 9.2 - Fusible interlinings are being used with...Ch. 9.2 - Damage to grapes from bird predation is a serious...Ch. 9.2 - The accompanying data consists of prices () for...Ch. 9.2 - The article The Influence of Corrosion Inhibitor...Ch. 9.2 - Anorexia Nervosa (AN) is a psychiatric condition...Ch. 9.2 - As the population ages, there is increasing...Ch. 9.2 - The article Effect of Internal Gas Pressure on the...Ch. 9.2 - The article Flexure of Concrete Beams Reinforced...Ch. 9.2 - Refer to Exercise 33 in Section 7.3. The cited...Ch. 9.2 - The degenerative disease osteoarthritis most...Ch. 9.2 - The article The Effects of a Low-Fat, Plant-Based...Ch. 9.2 - Consider the pooled t variable T=(XY)(12)sp1m+1n...Ch. 9.2 - Refer to Exercise 34. Describe the pooled t test...Ch. 9.3 - Consider the accompanying data on breaking load...Ch. 9.3 - Hexavalent chromium has been identified as an...Ch. 9.3 - Adding computerized medical images to a database...Ch. 9.3 - Scientists and engineers frequently wish to...Ch. 9.3 - Lactation promotes a temporary loss of bone mass...Ch. 9.3 - Antipsychotic drugs are widely prescribed for...Ch. 9.3 - Many freeways have service (or logo) signs that...Ch. 9.3 - Cushings disease is characterized by muscular...Ch. 9.3 - Refer back to the previous exercise. a. 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Does the data suggest that...Ch. 9.5 - Toxaphene is an insecticide that has been...Ch. 9.5 - The following observations are on time (h) for a...Ch. 9.5 - The article Enhancement of Compressive Properties...Ch. 9.5 - Reconsider the data of Example 9.6, and calculate...Ch. 9 - The accompanying summary data on compression...Ch. 9 - The article Supervised Exercise Versus Non-...Ch. 9 - Is the response rate for questionnaires affected...Ch. 9 - Shoveling is not exactly a high-tech activity, but...Ch. 9 - The article Quantitative MRI and Electrophysiology...Ch. 9 - The following summary data on bending strength...Ch. 9 - The article Urban Battery Litter cited in Example...Ch. 9 - The derailment of a freight train due to the...Ch. 9 - Headability is the ability of a cylindrical piece...Ch. 9 - The article Fatigue Testing of Condoms cited in...Ch. 9 - Information about hand posture and forces...Ch. 9 - The article Pine Needles as Sensors of Atmospheric...Ch. 9 - The article The Accuracy of Stated Energy Contents...Ch. 9 - Arsenic is a known carcinogen and poison. The...Ch. 9 - The accompanying data on response time appeared in...Ch. 9 - Acrylic bone cement is commonly used in total...Ch. 9 - In an experiment to compare bearing strengths of...Ch. 9 - How does energy intake compare to energy...Ch. 9 - An experimenter wishes to obtain a CI for the...Ch. 9 - A study was carried out to compare two different...Ch. 9 - Wait staff at restaurants have employed various...Ch. 9 - The paper Quantitative Assessment of Glenohumeral...Ch. 9 - Suppose a level .05 test of H0:12=0 versus Ha:120...Ch. 9 - The invasive diatom species Didymosphenia geminata...Ch. 9 - Researchers sent 5000 resumes in response to job...Ch. 9 - McNemars test, developed in Exercise 56, can also...Ch. 9 - The article Evaluating Variability in Filling...Ch. 9 - Let X1,, Xm be a random sample from a Poisson...Ch. 9 - Referring to Exercise 94, develop a large-sample...

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