SOLUTION: I'm having a hard time understanding how to compute this question. I'm just starting my summer school class and my teacher is absolutely HORRID! It's his first time ever teaching a

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Question 878490: I'm having a hard time understanding how to compute this question. I'm just starting my summer school class and my teacher is absolutely HORRID! It's his first time ever teaching and he doesn't speak english well!
My question is how do I solve this question?
Question:
WestCo tracks their daily profits and has found that the distribution of profits is approximately normal with a mean of $21,600.00 and a standard deviation of about $1,000.00. Using this information, answer the following questions. Round your intermediate answers (z-values) to 2 decimal places in order to be able to read the corresponding area values from the table.
For full marks your answer should be accurate to at least four decimal places.
Compute the probability that tomorrow's profit will be:
a) greater than $23,450.00
b) less than $21,290.00 or greater than $21,460.00
c) between $19,950.00 and $21,470.00 0

Answer by ewatrrr(24785)   (Show Source): You can put this solution on YOUR website!
 

Hi

Population: mean = 21,600, Sd = 1000

a) P(x > 23,450) = 1 - P(x ≤ 23,450) = 1 - P(z ≤ (23450-21600)/1000) 

                                  = 1 - P(z ≤ 1.85) = 1- .9678 = .0322 0r 3.22%

TI syntax is normalcdf(smaller, larger, µ, σ).

Using TI:  1 - normalcdf(-9999, 23450, 21600, 1000)

Note: The Placeholder -9999 is used as the smaller value to be at least 5 standard deviations from the mean.

b) Since this is a continuous function, we have  P(x < 21290) = P(x ≤ 21290).

P(21290 ≤ x ≤ 21460) = normalcdf(-9999. 21460, 21600, 1000) - normalcdf(-9999. 21290, 21600, 1000)

c) P(19950 ≤ x ≤ 21470)= normalcdf(-9999. 21470, 21600, 1000) - normalcdf(-9999. 19950, 21600, 1000)

 

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