The following appeared as part of an article in a health and beauty magazine.
'A group of volunteers participated in a study of consumer responses to the new Luxess face cream. Every morning for a month, they washed their faces with mild soap and then applied Luxess. At the end of that month, most volunteers reported a marked improvement in the way their skin looked and felt. Thus it appears that Luxess is truly effective in improving the condition of facial skin.'
The author claims that the new Luxess face cream is truly effective in improving the condition of facial skin. However, his assertion is unconvincing because it is merely based on a study which is not clearly presented.
First of all, the situation of respondents of the study is questionable. One the one hand, the author provides no specific information about situation the respondents. It is quite possible that this is a group composed of merely 10 or 20 persons. It is also quite possible that people in this group all have the same facial skin problem. If either is the case, the results of the study can hardly be applied to the wide population. One the other hand, the voluntary nature of the respondents renders the study unconvincing, because it means that the respondents are not generated using probability sampling, which is much more scientific.
Even if there is no problem about the respondents, the way the study is performed still is questionable. The author provides no information about whether other cosmetics were used. It is quite possible that other cosmetics were used and it is the other cosmetics that were responsible for the improvement of the facial skin. Even if no other cosmetic was used, the practice is still questionable because as the author stated, the respondents used the new Luxess face cream together with mild soap. Perhaps it is the mild soap that contributed to the improvement of the facial skin rather than the face cream. Besies that, the time span of the study--one month--is too short to lead to any convincing results.
Even if the study is carried out appropriately, the conclusion of the study is still problematic. Firstly, since the results were "reported", it is quite possible that those who felt no improvement would not report the effect of the face cream. It is also quite possible that the respondents felt that since they used a new face cream, their skin should be better. Secondly, the way the skin looks and feels is no scientific index for the condition of the facial skin. Perhaps although the facial skin looks and feels well, it is not healthy inside.
In sum, the claim is based on a problematic study which renders it unwarranted. To make his claim more convincing, the author should make a probability sampling, eliminate all the factors that will impact the credibility of the study during the studying process, and use more scientific index to measure the improvement.
[ Last edited by zmmary on 2005-7-21 at 21:42 ]作者: zmmary 时间: 2005-7-21 19:13:44