Function and Probability
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1. A new book is being released and a bookstore predicts that 70% of customers that walk through the door on the release day will purchase the book. If 30 customers walk through the door, answer the following: (MUST SHOW WORK)
A) What type of distribution function (name) is the model for this situation?
B) What is the expected number of requests for the new book (based on the 30 customers)?
C) What is the variance?
D) What is the probability that at most 20 people will want the book?
E) How many copies of the book should the bookstore have on hand, if the store wants the probability of not having enough books to satisfy the demand to be less than 5%?
2. The national population distribution of scores on a high school graduation equivalency test is normal with a mean of 75 and a standard deviation of 12 (on a scale of 1 to 100).
A) If a student is randomly selected, what is the probability this his score is less than 69?
B) If a sample of 16 students are taken from this distribution what is the probability that the mean of the sample will be less than 69?
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1) A building is purchased with a principal amount to pay down of $108000. The payments will be made in 20 EQUAL, end of year (not monthly!) installments. What are the equal installments if the annual interest rate is 10%?
The annual payments would represent an annuity that has a present value of $108,000, ...
Education
- BSc , Wuhan Univ. China
- MA, Shandong Univ.
Recent Feedback
- "Your solution, looks excellent. I recognize things from previous chapters. I have seen the standard deviation formula you used to get 5.154. I do understand the Central Limit Theorem needs the sample size (n) to be greater than 30, we have 100. I do understand the sample mean(s) of the population will follow a normal distribution, and that CLT states the sample mean of population is the population (mean), we have 143.74. But when and WHY do we use the standard deviation formula where you got 5.154. WHEN & Why use standard deviation of the sample mean. I don't understand, why don't we simply use the "100" I understand that standard deviation is the square root of variance. I do understand that the variance is the square of the differences of each sample data value minus the mean. But somehow, why not use 100, why use standard deviation of sample mean? Please help explain."
- "excellent work"
- "Thank you so much for all of your help!!! I will be posting another assignment. Please let me know (once posted), if the credits I'm offering is enough or you ! Thanks again!"
- "Thank you"
- "Thank you very much for your valuable time and assistance!"
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