1)Coal is carried from a mine in West Virginia to a power plant in New York in h
ID: 3052311 • Letter: 1
Question
1)Coal is carried from a mine in West Virginia to a power plant in New York in hopper cars on a long train. The automatic hopper car loader is set to put 82 tons of coal into each car. The actual weights of coal loaded into each car are normally distributed, with mean = 82 tons and standard deviation = 0.5 ton.
(a) What is the probability that one car chosen at random will have less than 81.5 tons of coal? (Round your answer to four decimal places.)
(b) What is the probability that 23 cars chosen at random will have a mean load weight x of less than 81.5 tons of coal? (Round your answer to four decimal places.)
2
(c) Suppose the weight of coal in one car was less than 81.5 tons. Would that fact make you suspect that the loader had slipped out of adjustment?
Yes No
Suppose the weight of coal in 23 cars selected at random had an average x of less than 81.5 tons. Would that fact make you suspect that the loader had slipped out of adjustment? Why?
Yes, the probability that this deviation is random is very small. Yes, the probability that this deviation is random is very large. No, the probability that this deviation is random is very small. No, the probability that this deviation is random is very large.
2)Consider an x distribution with standard deviation = 12.
(a) If specifications for a research project require the standard error of the corresponding x distribution to be 4, how large does the sample size need to be?
n = 1
(b) If specifications for a research project require the standard error of the corresponding x distribution to be 1, how large does the sample size need to be?
n = 2
Explanation / Answer
1a)
probability that one car chosen at random will have less than 81.5 tons of coal:
b)
probability that 23 cars chosen at random will have a mean load weight x of less than 81.5 tons of coal
c)No as probability of that is not very less
d)Yes, the probability that this deviation is random is very small.
2)
a) sample size =(std deviation/std error )2 =(12/4)2 =9
b) sample size =(std deviation/std error )2 =(12/1)2 =144
for normal distribution z score =(X-)/ here mean= = 82.000 std deviation == 0.5000Related Questions
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