1. A usability analyst is interested in evaluating a browser-based interface.
   She decides to conduct a controlled experiment and selects a sample of 
   seventeen users for observation. She provides them with a suite of tasks
   and observes the number of errors made in completing the task suite. She
   discovers that the mean error count is 15 with standard deviation of 8.
   Note: In each case make and state any necessary assumptions.

   a) Provide a point estimate for the mean error count of the population.
   b) Determine the margin of error for your estimate of the population mean.
   c) Construct and interpret an 80% confidence interval for the population 
      mean. 
   c) Construct and interpret a 99% confidence interval for the population 
      mean. 
 
2. Consider the database performance problem. You would like to estimate
   the mean wait time of transactions processed on a particular day to a 
   level of accuracy of 1.5ms. 

   a) You select a small sample of transactions and discover that the standard
      deviation is 10ms. Determine the minimum sample size required in each 
      case below.
      i) The level of confidence is 90%. 
     ii) The level of confidence is 99%. 
   b) You are unable to selct a small sample (as done above) but know from 
      experience that wait time ranges between 4ms and 36ms. Use this
      fact to determine the minumum sample size needed to estimate the
      mean wait time if the level of confidence is 95%.