Alguns exemplos onde a variação está presente no dado podem ser encontrados em Landim (1997).
Maximal static inspiratory pressure (PImax) is an index of respiratory muscle strength. The following data show the age (years) and a measure of PImax (cm HO) for 25 cystic fibrosis patients.
Scientists measured the fat and protein content in milk samples from 10 grey seals.
The table below shows the results of an experiment where the researchers were interested in the role of nitrogen, magnesium and certain micro-nutrients in the metabolism of sunflowers. Twelve sunflower plants were grown in water culture for nine weeks, under uniform conditions of lighting and temperature. Each plant was in a separate pot with one type of culture solution. There were four batches of three plants: A, B, C, D. The three plants in Batch A were grown in a complete culture solution. Those in Batch B had the same culture solution except that it lacked magnesium. The solution for Batch C lacked only nitrogen and that for Batch D lacked only th micronutrients (boron, manganese, zinc and copper). At the end of the experiment each plant was chopped up, dried in an oven and then weighed, giving the results in the table.
One of the earliest recorded comparative biomedical trials (c. 597 B.C.) is a nutritional experiment from the Book of Daniel in the bible. The background is that Daniel was held hostage, and disapproved of the rich food, wine, and meat served. In order to convince the guard in charge that he and his three friends should be given a simple diet of vegetables, Daniel asked for a 10-day trial. He promised to eat the assigned diet if those on the vegetable diet weren't as healthy as the others.
Then Daniel said to the guard ``Submit us to this test for ten days. Give us only vegetables to eat and water to drink; then compare our looks with those of the young men who have lived on the food assigned by the king, and be guided in your treatment of us by what you see.'' The guard listened to what they said and testedn them for ten days. At the end of the ten days they looked healthier and were better nourished than all the young men who had lived on the food assigned to them by the king. So the guard took away the assignment of food and the wine they were to drink and gave them only vegetables.Chapter 1, Verses 12-15, New English Bible Version.
What do you think of Daniel's experiment? That is, are you convinced that the vegetable diet is better? Why or why not?