Tham khảo tài liệu 'data analysis and presentation skills part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | STATISTICALTESTS FORTWO SAMPLES 121 Student t-test for dependent matched paired samples Maintaining variability at as low a level as possible is an important consideration in the design of experiments. One means of minimizing variability is to design an experiment on a paired or matched basis. Imagine we want to examine the efficacy of a new long-acting formulation of aspirin Z with a standard compressed tablet preparation Y . We could recruit eight patients who would be willing to participate in the experiment but there is likely to be many factors that vary within the patient group - they are all not going to be the same height weight or age have the same state of health or have symptoms of exactly the same severity. What rules can we apply to the experimental conditions to ensure that these factors are minimized 1. Each patient can have administered on separate occasions the new formulation and the standard aspirin preparation. As the assessment of the efficacy of the treatment will be carried out by the patients themselves any intra-subject variability will be eliminated by generating matched data. 2. Bias may be removed from the experiment by adopting a double-blind technique. The order in which the preparations are administered can be randomized four patients will receive aspirin on the first occasion whilst the remaining four will receive the new drug and the experiment will be double-blind. A double-blind design means that both treatments will be coded Yor Z so that neither the patient receiving the medication nor the doctor giving the tablets will be able to identify which treatment is being given. The code for the treatment is kept by a third independent party. Section discusses study designs to eliminate bias. At the end of the experiment the investigator will have an assessment of the number of hours of pain relief from the patients. In the experiment we have generated paired data as the subjects have acted as their own control. The paired t-test .