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Homework #3
ME 236
I. Review Questions (Not Due)
1. True or False:
a. All random measurements are normally distributed.
b. Using the z value in confidence intervals presumes that the population standard
deviation is known.
c. Approximately 92% of all data in a normal distribution lie within ±1.75 standard
deviations from the population mean.
2.
When predicting the mean of a population based on the mean of a sample (the population
standard deviation is known), what happens to the confidence interval when the sample
size approaches infinity? Circle all that apply:
a. the confidence interval approaches a finite value
b. the confidence interval approaches zero
c. the z value approaches 1.96
d. the confidence interval approaches infinity
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3. Evaluate the integral: f ( x) 
e
6 0.5 x 2
dx . Hint: e a b  e a e b . Do so without any integration
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functions on your calculator.
II. Homework (Due)
Turn in the following 4 problems from the book, plus the extra Problem 3-A below.
3-2, 4, 6, 8, 10
Problem 3-A. A voltmeter is used to measure a known voltage of 100 V. Forty percent of the
readings are within 0.5 V of the mean value.
a. Assuming a normal distribution for the error, estimate the standard deviation for the
meter.
b. What is the probability that the mean of 10 readings will have an error greater than 0.75
V?