Finding probability, given μ and σ (Statistics)?
I need help on this problem, please help. I dont know why I cant think of the answer right now. Can you please explain the answer too so that I can grasp it?
With a mean of 38,000 sales per day. And a standard deviation of 10,000. Assuming the distribution is normal,
a. Find the probability that John has more than 41,000 sales in one day.
b. Find the probability that John makes between 35,500 and 41,000 sales in one day.
c. Suppose that special overflow parking lots are opened for the days with the highest 10% attendance levels. What is the cutoff attendance number that triggers the opening of the overflow parking areas?
d. If John only makes 16,000 sells. Is this unusual? On what do you base your answer?
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Figure out the number of standard distributions away from the mean any value is. Then look that up in a table of the standard normal distribution to find the probability. [z = (x - μ)/σ]
Example:
a. 41,000 - 38,000 = 3,000; 3,000/10,000 = 0.3 This value of z => 11.8%
See the table at: http://www.mathsisfun.com/data/standard-normal-dis...
b. 35,000 is 0.3σ below the mean for a probability also of 11.8%. The probability that John makes between 35,500 and 41,000 sales in one day = 11.8 + 11.8 = 23.6%
c. Missing information
d. z = 2.2. P = 0.5 - 0.486 = 0.014. a 1.4% probability would make it quite unusual.