Probability and Statistics for Engineering and the Sciences
9th Edition
ISBN: 9781305251809
Author: Jay L. Devore
Publisher: Cengage Learning
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Chapter 9, Problem 80SE
Arsenic is a known carcinogen and poison. The standard laboratory procedures for measuring arsenic concentration (mg/L) in water are expensive. Consider the accompanying summary data and Minitab output for comparing a laboratory method to a new relatively quick and inexpensive field method (from the article “Evaluation of a New Field Measurement Method for Arsenic in Drinking Water Samples,” J. of Envir. Engr., 2008: 382–388).
Two-Sample T-Test and CI
| Sample | N | Mean | StDev | SE Mean |
| 1 | 3 | 19. 70 | 1.10 | 0 . 64 |
| 2 | 3 | 10 . 90 | 0 . 60 | 0 .35 |
| Estimate for difference: 8.800 | ||||
| 95% Cl for difference: (6.498, 11.102) | ||||
| T-Test of difference = 0 (vs not =) : | ||||
| T-Value =12.16 P-Value =0.001 DF = 3 | ||||
What conclusion do you draw about the two methods, and why? Interpret the given confidence interval. [Note: One of the article’s authors indicated in private communication that they were unsure why the two methods disagreed.]
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The authors of the paper "Statistical Methods for Assessing Agreement Between Two Methods of Clinical Measurement"† compared two different instruments for measuring a person's ability to breathe out air. (This measurement is helpful in diagnosing various lung disorders.) The two instruments considered were a Wright peak flow meter and a mini-Wright peak flow meter. Seventeen people participated in the study, and for each person air flow was measured once using the Wright meter and once using the mini-Wright meter.
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Suppose that the Wright meter is considered to provide a better measure of air flow, but the mini-Wright meter is easier to transport and to use. If the two types of meters produce different…
The authors of the paper "Statistical Methods for Assessing Agreement Between Two Methods of Clinical Measurement"† compared two different instruments for measuring a person's ability to breathe out air. (This measurement is helpful in diagnosing various lung disorders.) The two instruments considered were a Wright peak flow meter and a mini-Wright peak flow meter. Seventeen people participated in the study, and for each person air flow was measured once using the Wright meter and once using the mini-Wright meter.
Subject
Mini-WrightMeter
WrightMeter
Subject
Mini-WrightMeter
WrightMeter
1
512
494
10
445
433
2
430
395
11
432
417
3
520
516
12
626
656
4
428
434
13
260
267
5
500
476
14
477
478
6
600
557
15
259
178
7
364
413
16
350
423
8
380
442
17
451
427
9
658
650
(a)
Suppose that the Wright meter is considered to provide a better measure of air flow, but the mini-Wright meter is easier to transport and to use. If the two types of meters produce…
The authors of the paper "Statistical Methods for Assessing Agreement Between Two Methods of Clinical Measurement" compared two different instruments for measuring a subject's ability to breathe out air.† (This measurement is helpful in diagnosing various lung disorders.) The two instruments considered were a Wright peak flow meter and a mini-Wright peak flow meter. Seventeen subjects participated in the study, and for each subject air flow was measured once using the Wright meter and once using the mini-Wright meter.
Subject
Mini-WrightMeter
WrightMeter
Subject
Mini-WrightMeter
WrightMeter
1
512
494
10
445
433
2
430
395
11
432
417
3
520
516
12
626
656
4
428
434
13
260
267
5
500
476
14
477
478
6
600
557
15
259
178
7
364
413
16
350
423
8
380
442
17
451
427
9
658
650
(a)
Suppose that the Wright meter is considered to provide a better measure of air flow, but the mini-Wright meter is easier to transport and to use. If the two types of meters produce…
Chapter 9 Solutions
Probability and Statistics for Engineering and the Sciences
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