Week 6: Homework Assignment 3

Instructions:
1. Show your complete work. You may manually calculate or use Excel/PhStat. The
PhStat output, if adequately labeled, is enough to meet the work required.
2. You may submit a word or excel file. Do not convert to pdf unless it is
handwritten.
Problem 1. 4 points
The number of arrivals per minute at a bank located in the central business district of a
large city was recorded over a period of 150 minutes, with the following results:
Arrivals Frequency
0 15
1 20
2 30
3 45
4 25
5 10
6 5
a. Compute the expected number of arrivals per minute.
b. Compute the standard deviation
Problem 2. 8 points
A student is taking a multiple-choice exam in which each question has five choices.
Assume that the student has no knowledge of the correct answers to any of the questions.
She has decided on a strategy in which she will place five balls (marked A, B, C, D and
E) into a box. The marking on the ball will determine her answer to the question. There
are 10 multiple choice questions on the exam. What is the probability that she will get:
a. 10 questions correct?
b. At least four questions correct?
c. No more than 3 questions correct?
d. At least 3 but no more than 7 questions are correct?
Problem 3. 8 points
The mean number of new visitors to the website is 24.0 per minute. Twenty-five
percent of these visitors buy at least one product from the website. What is the
probability that in any given minute:
a. Zero new visitors will arrive at the website and buy at least a product?
b. Exactly five new visitor will arrive at the website and buy at least a product?
c. Two or more new visitors will arrive at the website and buy at least a product?
d. At least three but not more than 9 new visitors will arrive at the website and buy
at least a product?

Tutorial for Homework Assignment