In: Statistics and Probability
Should you generate electricity with your own personal wind turbine? That depends | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
on whether you have the right amount of wind on your site. For a personal wind | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
turbine to work properly, your site should have an annual average wind speed of at | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
least 10 miles per hour, according to the Wind Energy Association. Lower winds do | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
not provide enough energy. One candidate site was monitored last year, with wind | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
speeds recorded every 8 hours. A total of 49 readings of wind speeds average 9.56 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
mph with a standard deviation of 2.52 mph. You've been asked to make a statistical | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
report to help the landowner decide whether to place a wind turbine at the site. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Test whether the average wind speed is at least 10 mph at the .025 level of | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
significance. Show Your Work! Formula(s), Substitutions, Answers! Round your critical | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
value to 3 decimal places, and your pvalue to 4 decimal places.
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ANSWER
1)
(7) = 1- (0.16 + 0.2 + 0.36) = 0.28
mean = 3 * 0.16 + 6 * 0.2 + 7 * 0.28 + 12 * 0.36
= 7.96
std.deviation = summation (sqrt(x - mean)^2*P(x))
= Below are the null and alternative Hypothesis,
Null Hypothesis, H0: μ = 10
Alternative Hypothesis, Ha: μ < 10
Rejection Region
This is left tailed test, for α = 0.025 and df = 48
Critical value of t is -2.011.
Hence reject H0 if t < -2.011
Test statistic,
t = (xbar - mu)/(s/sqrt(n))
t = (9.56 - 10)/(2.52/sqrt(49))
t = -1.222
P-value Approach
P-value = 0.1138
As P-value >= 0.025, fail to reject null
hypothesis.
2)
since p value >0.05. we fail to reject the null hypothesis
Type II Error is correct option , since we fail to reject a false null hypothesis
3)
Rejection Region
This is left tailed test, for α = 0.05 and df = 48
Critical value of t is -1.677.
Hence reject H0 if t < -1.677
Test statistic,
t = (xbar - mu)/(s/sqrt(n))
t = (9.56 - 10)/(2.52/sqrt(49))
t = -1.222
P-value Approach
P-value = 0.1138
As P-value >= 0.05, fail to reject null hypothesis.
At the .05 level of significance, the site ( is not)
suitable for a small wind turbine.
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