Sam's+design+Block+F+2011

Your friend insists that he can tell the difference between expensive bottled water and ordinary tap water. Design a study to test this assertion.

 * Hypothesis:** A person will not be able to tell the difference between expensive bottled water and ordinary tap water if they are poured into two glasses of water that are exactly the same.


 * Independent variable: Amount of caffeine in the drink. Type of drink consumed (coffee). Amount of beverage consumed (200 ml.) Time consumed prior to taking the test (30 minutes). Type of test (PSAT). Length of test (two hours). Number of students participating (120).
 * Dependent variable: results of the exam.
 * Students taking this test will be those that have not yet taken a PSAT and are 15 years of age. Random selection with roughly equal numbers of girls and boys, though this should not be a problem.
 * This will be a double blind study so that those providing the beverages will not influence the test one way or another. This is to avoid self-fulfilling prophecy. Half of the students will be given a caffeine drink; the other half will be given a placebo.
 * The results will be compared. Must seek to find if the difference in performance, if one exists, is due to the independent variable and not to error or chance occurrence (see p.614 Appendix A of //Introduction to Psychology 8e//)

How can this study be sure that the students getting the caffeine drink and doing exceptionally well on the exam were not gifted students? Would not a better study compare students to themselves? Doing this would require an exam format that contains different style of questions, but with the same level of difficulty. The study sample is too small to know if this can be true for everyone. As well you failed to state the time of day in which this study would take place. We know, for example, that student performance early in the morning may not be as good as student performance later in the day.
 * CRITIQUE:**