Statistics Cases

a) What is the response variable and what is the factor?

b) Ho many levels of the factor are being studied?

c) Is there any difference in the average time to failure of the disks from the 3 different suppliers? If so, which ones are different?

d) What is your recommendation to the company and why?

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14.2

A company had received complaints that the disks provided by the company
failed to work properly after extended use. The company has decided to
investigate the complaint. Data are collected on the time to failure
for disks from their current supplier and two alternate suppliers. The
data are shown below:

Current supplier Alternative 1 supplier Alternative 2 supplier

486 489 508

490 489 510

491 491 517

491 492 506

494 492 515

494 492 520

496 492 503

498 493 524

498 493 515

502 494 503

504 495 507

505 496 515

506 497 509

507 497 518

508 497 495

510 498 499

514 499 510

515 502 503

527 503 533

498 505 517

What is the response variable and what is the factor?

Ho many levels of the factor are being studied?

Is there any difference in the average time to failure of the disks from
the 3 different suppliers? If so, which ones are different?

What is your recommendation to the company and why?

14.3

Grading homework is a real problem. It takes an enormous amount of time
and many students do not do a very good job. A teacher of elementary
statistics decided to conduct a study to determine what effect grading
homework had on her student’ exam scores. She taught 3 sections of
Elementary Statistics and randomly assigned each class one of three
conditions: 1) no homework given, 2) homework given but not collected,
and 3) homework given, collected and graded. After the first exam, she
collected the data (exam scores). They are shown below:

No Homework Homework not collected Homework collected,

69 73 83

69 63 97

92 68 72

84 79 79

79 57 84

84 68 76

76 72 91

63 74 76

76 49 83

82 84 88

89 79 91

72 71 96

72 80 68

65 74 99

73 71 89

47 63 80

92 88 79

71 83 91

83 89 83

81 82 83

92 69 76

80 92 90

64 79 79

72 81 67

84 76 86

79 81 86

74 81 82

81 75 84

What is the response variable and what is the factor?

How many levels of the factor are being studied?

Is there any difference in the average exam scores using the 3 different
approaches to homework? If so, which ones are different?

What is your recommendation to the teacher and why?

The sports industry is a large and competitive market. A manufacturer
of golf balls is considering 4 new ball designs. A sample of 36 balls
from each of the 4 models is tested and the distance the balls carry (in
yards) is recorded. The balls are hit by a machine. The data are shown
below.

M1 Model M2 Model M3 Model M4 Model

257 256 244 250

255 255 243 255

256 258 241 251

255 257 243 249

255 257 240 250

256 257 249 251

255 258 244 251

258 258 249 248

252 256 248 247

256 258 243 253

253 258 242 250

254 256 245 255

260 259 253 250

258 255 250 256

258 259 251 260

257 257 249 259

259 256 249 252

257 255 249 253

255 255 255 257

256 257 249 255

259 260 251 251

261 255 250 255

260 261 248 253

257 262 250 255

260 258 258 262

262 260 258 258

258 260 257 263

260 256 258 259

258 255 254 256

258 256 256 261

258 257 255 258

256 251 254 258

260 253 255 256

260 254 260 263

261 254 254 264

257 255 253 257

What is the response variable and what is the factor?

How many levels of the factor are being studied?

Is there any difference in the average distance the ball carries?

What is your recommendation to the company and why.