Business Statistics

Instructions: Remember to show your work if an answer requires a mathematical solution.

1. When the owner of a small business reviews her list of contracts for 2011, she finds that 35% of the contracts were from clients she met at a large conference at the end of 2010. Answer the following questions about this situation.

a. Was this measurement obtained by a sample or a census? What words in the description of the situation make you confident that your answer is correct?

b. Should the owner have taken into account some measure of reliability associated with the value 35%?

2. Assume that the number of sales per day of a app in the Apple iOS App Store is normally distributed.

a. What two parameters of the distribution would you need to be able to determine the probability of sales on a particular day exceeding 100 units?

b. If the probability of sales exceeding 100 units is 20% and the mean daily sales is 86 units, then what is the standards deviation of the distribution?

3. Researchers are studying a new chemical process for producing dyes. Although they don't know it, the yield of the process is normally distributed with µ=550kg and Ó = 75kg. The researchers plan to estimate the process's mean yield by running enough sample to be 90% confident that their computed mean will be within 20kg of the actual mean? Show your work to justify your answer.