The Wall Street Journal reported on a study of holiday weight gain. Researchers assessed weight gain by asking people how much weight they typically gain in the fall and winter (Parker-Pope, 2005). The average answer was 2.3 kilograms. But a study of actual weight gain over this period found that people gained, on average, 0.48 kilogram. 

a. Is the method of asking people about their weight gain likely to be reliable? Explain. 

b. Is this method of asking people about their weight gain likely to be valid? Explain.