(3 pts.) 3. A researcher wants to know the effect of eating certain types of food on the ability to concentrate. Therefore. she randomly assigns 120 college students to one of three groups: vegetarian, high protein, or high carbohydrate. Before the diet change, she gives each student a concentration test. After 3 months of the speciﬁc diet, she re-administers the test and records the change in test scores. (1 pt.) a) Draw the correct experimental design of this study. (1 pt.) b) Describe a possible methodology that could be used to decide which students will be assigned to which diet. (1 pt.) o)
Is this study well-designed? If not, how would you change the design method? Please explain your answer. (1 pt.) 4. An instructor wants to know whether freshmen and sophomores respond differently to the different teaching methodologies, traditional lectures or active leaming. After the study is over, she conducts a survey to determine the response. Draw the correct design for this experiment. Hint: In the design, it is better to start off with the teaching methodology. Remember to clearly indicate what is randomized. (1 pt.) 5. Researchers want to determine which diet is better in controlling blood sugar in diabetes; the normal low carbohydrate diet or a keto diet (no carbohydrates). Consider the following observational study and experiment: Observational study One researcher ﬁnds 100 Type II diabetic women who have been using the normal low-carbohydrate diet for at least one year and no other methods of controlling diabetes. in addition. he ﬁnds another 100 Type II diabetic women who have been using the keto diet for at least one year and no other methods of controlling diabetes. The researcher records the average fasting blood sugar value (seven readings). Experiment Another researcher ﬁnds 200 Type II diabetic women who are not taking any drugs (including insulin) for controlling diabetes. She randomly assigns 100I of the women to the normal low carbohydrate diet and the other 100 women to the keto diet. The researcher records the average fasting blood sugar value (seven readings) before the diet change and again one-year later. Which of the two, the given observational study or the given experiment, gives better information about the relationship between these diets and fasting blood sugar?