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Three engineers are independently estimating the spring
Chapter 7, Problem 10E(choose chapter or problem)
Three engineers are independently estimating the spring constant of a spring, using the linear model specified by Hooke’s law. Engineer A measures the length of the spring under loads of 0, 1, 3, 4, and 6 lb, for a total of five measurements. Engineer B uses the same loads, but repeats the experiment twice, for a total of 10 independent measurements. Engineer C uses loads of 0, 2, 6, 8, and 12 lb, measuring once for each load. The engineers all use the same measurement apparatus and procedure. Each engineer computes a 95% confidence interval for the spring constant.
a. If the width of the interval of engineer A is divided by the width of the interval of engineer B, the quotient will be approximately__________ .
b. If the width of the interval of engineer A is divided by the width of the interval of engineer C, the quotient will be approximately__________ .
c. Each engineer computes a 95% confidence interval for the length of the spring under a load of 2.5 lb. Which interval is most likely to be the shortest? Which interval is most likely to be the longest?
Questions & Answers
QUESTION:
Three engineers are independently estimating the spring constant of a spring, using the linear model specified by Hooke’s law. Engineer A measures the length of the spring under loads of 0, 1, 3, 4, and 6 lb, for a total of five measurements. Engineer B uses the same loads, but repeats the experiment twice, for a total of 10 independent measurements. Engineer C uses loads of 0, 2, 6, 8, and 12 lb, measuring once for each load. The engineers all use the same measurement apparatus and procedure. Each engineer computes a 95% confidence interval for the spring constant.
a. If the width of the interval of engineer A is divided by the width of the interval of engineer B, the quotient will be approximately__________ .
b. If the width of the interval of engineer A is divided by the width of the interval of engineer C, the quotient will be approximately__________ .
c. Each engineer computes a 95% confidence interval for the length of the spring under a load of 2.5 lb. Which interval is most likely to be the shortest? Which interval is most likely to be the longest?
ANSWER:
Step 1 of 4
(a) Engineer A and Engineer B measure the length of the spring under the same loads.
The width of the confidence interval for the slope (spring constant) is twice the margin of error.
Since the two engineers use the same springs and loads, it is safe to assume that the standard deviation is the same for the two engineers.