[文学]research_design.pptVIP

Basic question: does A cause B? The fundamental requirement of an experimental design: the researcher has some control over variation in the independent variable and is able to control the influence of other variables.控制自变量的变化，同时也要减少其他变量的影响。 Company Logo Company Logo Lessons on nutritious snacks Healthier snacks selected + Company Logo Time 1 Time 2 1. Select two groups of students. 2. Devise measures for the variables. 3. Select one of the two classes of home economics students to be the control group对照组，控制群which will have lessons on else, while the experimental group will have lessons on nutritious snacks. Company Logo 4．The dependent variable will be measured before and after the lessons are given to both the control and the experimental group 5．Because the groups are as alike as possible in all other respects and the only known difference is the exposure (or lack of it) to the lessons on nutritious snacks, any difference on snack selection can be attributed to the lessons on nutritious snacks. Company Logo Company Logo Student snack selection at tuck-shop 1 : The lessons have effect Company Logo Before After A(Exp) B(control) A(Exp) B(control) Sweets 70% 70% 50% 70% Fruits 20% 20% 40% 20% other 10% 10% 10% 10% Student snack selection at tuck-shop 2: The lessons have no effect Company Logo Before After A(Exp) B(control) A(Exp) B(control) Sweets 70% 70% 60% 60% Fruits 20% 20% 30% 30% other 10% 10% 10% 10% Company Logo Hours of study Marks on history test Comprehension is treated as one aspect of academic performance Company Logo 45 minutes study time 45 minutes study time Average results on comprehension tests for two classes 1 Company Logo Condition 1 Condition2 Experimental group 60% 80% Control group 60% 60% Condition 1 Condition2 Experimental group 65% 70% Control group 60% 65% Average results on comprehension tests for two classes 2 Average results on comprehension tests for two classes 3 Condition 1 Condition2 Experimental gro