Stats Unit 3

Total points are 30. Points are included with each problem.
Included with each section or problem are reference examples and end of section exercises that can be used as a guide. Be sure to show your work so that partial credit may be awarded. To receive full credit, work must be shown if applicable.

Section 3.1: Basic Concepts of Probability and Counting

1. Lock combinations are made using 3 digits followed by 2 letters. How many different lock combinations can be made if repetition of digits is allowed? (References: example 4 page 135, end of section exercises 13 - 16 page 142 and 35 – 36 page 144) (6 points)

Answer

Three digits are given with a 2 letters. The total number of objects is 5. The repetition of digits is allowed.
Hence the total number of permutation of digits is, 53 = 125

The repetitions of letters is not allowed,

Therefore 2 letters can be permutated as, [pic]
Hence the total number of lock combinations is, 125*20 = 2500.

2. In 2001 the stock market took some big swings up and down. One thousand investors were asked how often they tracked their investments. The table below shows their responses. What is the probability that an investor tracks the portfolio weekly? (References: example 6 page 137, end of section exercises 45 - 48 page 145) (5 points)

|How often tracked? |Response |
|Daily |235 |
|Weekly |278 |
|Monthly |292 |
|Few times a year |136 |
|Do not track | 59 |

Answer
We have given that,

|How often tracked? |Response |
|Daily |235 |
|Weekly |278 |
|Monthly |292 |
|Few times a