31 A study was conducted of the effects of a special class designed to improve children's verbal skills. Each child took a verbal skills test twice. both before and after a three-week period in the class. Let Y be the second exam score minus the first exam score. Ilence, if (the population mean for Y') is equal to 0, the class has no effect on the average. Test the null hypothesis of no effect against the alternative hypothesis that the effect is positive, if the scores on Y for a random sample of four children having leaming problems were 3. 7.3.3. Interpret the P-value. (Note. The scores could tend to improve simply from the students feeling more comfortable with the testing process. A more appropriate design would also administer the exam twice to a control group that does not take the special class. comparing the changes for the experimental and control groups.)