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t-test Problems

• The datasets for these problems are found in the Excel file t-test1.xls.
  
  1. In 1998, as an adverting campaign, a cookie company claimed that every 18-ounce bag contained an an average of 1000 chocolate chips. Students at the Air Force Academy in Colorado Springs bought some randomly selected bags of cookies and counted the chocolate chips. Some of their data are recorded on the ChocolateChips dataset of the Excel file.
     
     1. Form the normal plot of the chocolate chip counts. Are the counts normally distributed?
     2. Perform a 99%-level test of hypothesis that the average chocolate chip count is 1000 per bag.
  2. Psychology experiments involve testing the ability of rate to navigate mazes. The mazes are classified according to difficulty, as measured by the average length of time it takes rats to find the food at the end. One researcher needs a maze that will take rats an average of about one minute to solve. He tests one maze on several rats, collecting the data on the RatMaze spreadsheet in the Excel file.
     
     1. Form the normal plot and box plot of the maze times. Are the times normally distributed?
     2. Test the hypothesis that the true completion time is one minute.
     3. Eliminate the outlier and perform the hypothesis test again.
  3. A food company marks the net weight of their potato chip bags as 28.3 grams. To test whether this claim is true, students collect and measure the net weights of bags. The measurements are recorded on the PotatoChipBags spreadsheet in the Excel file.
     
     1. Form the normal plot of the new weights of the potato chip bags. Are the weights normally distributed?
     2. Test the hypothesis that the true weight of potato chip bags is 28.3 grams.