Lab experiment: takes place in a laboratory and often involve typothetical scenariosFiel experiment: takes place in the natural environment and involves “real” decisionsIs the experimental design any good?• Internal validity– The manipulation of the independent variable is the real cause of the observed effects– The degree to which the effects of extraneous variables are controlled• External validity– Can the effects found be generalized in reality? 所发现的影响能否在现实中得到普遍化– It often comes down to lab vs. field experiments (more on this later)– Do the target population and test units match? 目标人群和测试是否匹配
Factors that cause poor internal validity – the different extraneous variables (EV)!• Poorly designed experimental stimuli 设计不当的实验刺激• Treatment and control groups are not randomly assigned 处理和对照组不是随机分配的• Treatment and control take place at different time (external events) 处理和对照发生在不同的时间Post test only control group design has the most internal validity than static group design and one group pretest-posttest.Limitations of Experimentation• Time consuming• Expensive• Difficult to administer• Competitors may deliberately contaminate the results of a field experiment
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