看了题目后我想到的3个方向:
1。样本太小。这些人能否代表Luxess的客户群。
2。respondents=all of the test takers? 也许只有收到效果的顾客才去反馈表示感谢呢?
3。皮肤的改善可能是mild soap所引起。
4。短时间的改善是否等于长期使用的效果?长期使用有没有副作用?
Several variables have been ruled out of this survey which, if included, would make the author's assertion more valid. For instance, the author fails to guarantee us that respondents are the representatives of all the consumers .
(The author fails to guarantee us that the group of respondents can typify that of the entire Luxess's targetted customers.)这样似乎清楚一点。
我结合自己的想法和楼上各位的意见,总结了一下:
survey:
1volunteers is representative or not
2 conducted method is valid or not (random sampling principle)
3 result is credible or not (the relationship with company)
4 criterion of marked improvement is vague
causal relation:
1 effect of soft soap (it may be the primary reason)
2 time needed to justify its effect