14、An analyst determined that approximately 99 percent of the observations of daily sales for a company were within the interval from $230,000 to $480,000 and that daily sales for the company were normally distributed. The mean daily sales and standard deviation of daily sales, respectively, for the company were closest to:

A. Answer A

B. Answer B

C. Answer C

D. Answer D

[此贴子已经被作者于2008-11-7 16:47:30编辑过]

Correct answer = C

"Common Probability Distributions," Richard A. Defusco, Dennis W. McLeavey, Jerald E. Pinto, and David E. Runkel
2008 Modular Level I, Vol. 1, pp. 391-392
Study Session 3-9-g
construct and interpret a confidence interval for a normally distributed random variable, and determine the probability that a normally distributed random variable lies inside a given confidence interval
Given that sales are normally distributed, the mean is centered in the interval.
Mean = ($230,000 + 480,000) / 2 = $355,000
An interval including 99% of the observations extends three standard deviations either side of the mean. The standard deviation of daily sales = ($355,000 - 230,000) / 3 = $41,667. 

[此贴子已经被管理员于2008-5-17 18:24:35编辑过]

thanks

thanks

thanks