Question 148777
Sixty wind speed readings gave an average velocity of x(bar)=1075 cm/sec. Based on long term experience, sigma (standard deviation)can be assumed to be 265 cm/sec. 
Find a 95% confidence interval for the population mean wind speed at this site AND does the confidence interval indicate that the population mean wind speed is such that the sand is always moving at this site. Explain.
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E = 1.96*265/(sqrt(60)) = 1.96*34.211 = 67.05
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95% CI: (1075-67.05 < u < 1075+67.05)
 = (1007.95 < u < 1142.05)
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The CI says we are 95% confident that the population average of wind
speeds is between 1007.95 and 1152.05. Since this entire interval 
is above 1000 we can be 95% confident that the sand is moving.
But this on the average.  There may be many times when the wind speed
is below 1000.
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Cheers,
Stan H.