Question 482955
A machine puts plastic into sheets that are 30 feet(360 inches)long. Assume that the population of lengths is normally distrubuted. 
Complete parts (a) and (b)
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a) The company wants to estimate the mean length the machine is cutting the plastic within 0.25 inc. Determine the minimum sample size required to construct a 95% confidence interval for the population mean. Assume the population standard deviation is 0.50 inch.
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n= [z*s/E]^2
n = [1.96*0.50/0.25]^2
n = 16 when rounded up
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b) Repeat part (a) using an error tolerance of 0.125 inc.
n= {1.96*0.50/0.125]^2  
n = 62 when rounded up
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Which error tolerance requires a larger sample size? Explain. 
A The tolerance E= 0.125 inch requires a larger sample size. As error size increases, a larger sample must be taken to ensure the desired acuracy.
B. The tolerance E=0.25 inch requires a larger sample size. As erro size increases a larger sample must be taken to ensure the desired accuracy. 
C. The tolerance E=0.25 inch requires a larger sample size. As error size
decreases, a larger sample must be taken to ensure the desired accuracy. 
D. The tolerance E = 0.125 inch requires a larger sample size. As error size decreases, a larger sample must be taken to ensure the desired accuracy.
0 solutions
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Answer: D ; Error size and sample size are indirectly related.
As the amount of allowed error decreases the sample size must rise.
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Cheers,
Stan H.
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