EXAMPLES OF T-TEST

One-Sample T Test  The One-Sample T Test procedure tests whether the mean of a single variable differs from a specified constant. Example: A researcher might want to test whether the average IQ score for a group of students differs from 100. Rahul Chandra

One-Sample Two tail test  Example: A cereal manufacturer sells its products in small packed bags weighing 1.5Kg. The packing is done by automated filling machine, set to pack 1.5 kg. The manufacturer may be interested to check whether the weight of the packed bags differs from the targeted weight of 1.5 kgs. Rahul Chandra

One-Sample one tail test  Example: You are the manager operations of a fast-food restaurant. You have devised a system where time to serve food should not be more than 4.5 minutes. Now you want to determine whether the system is effectively serving its purpose. In other words, mean waiting time to place an order is less than or equal to 4.5 minutes. Rahul Chandra

One-Sample one tail test  Example: A company that makes processed cheese is interested in determining whether some suppliers that provide milk for the processing operation are adding water to their milk to increase the amount supplied to the processing operation.  It is known that excess water reduces the freezing point of the milk. The freezing point of natural milk is normally distributed, with a mean of Celsius (C). The standard deviation of the freezing temperature of natural milk is known to be C. Because the cheese company is only interested in determining whether the freezing point of the milk is less than what would be expected from natural milk, the entire rejection region is located in the lower tail of the distribution. Rahul Chandra

Independent Samples T Test  Example: An analyst at a department store wants to evaluate a recent credit card promotion. To this end, 500 cardholders were randomly selected. Half received an ad promoting a reduced interest rate on purchases made over the next three months, and half received a standard seasonal ad; it may be of interest to see whether both the promotional methods have yield same results or they differ significantly. Rahul Chandra

Independent Samples T Test  Example In a sample of 400 women shoppers from the Mall A, the weekly expenditure on foods was found to be Rs250/- with a standard deviation of Rs40/-. The same figures are Rs220/- and Rs55/- in the Mall B where again a sample of 400 women shoppers is taken at random. Test at 1% significance level whether the weekly expenditure in both the Malls is equal. Rahul Chandra

Paired Samples T Test  Example: A physician is evaluating a new diet for her patients with a family history of heart disease. To test the effectiveness of this diet, 16 patients are placed on the diet for 6 months. Their weights and triglyceride levels are measured before and after the study, and the physician wants to know if either set of measurements has changed. Rahul Chandra