experimental-study.ppt

《experimental-study.ppt》由会员分享，可在线阅读，更多相关《experimental-study.ppt（11页珍藏版）》请在得力文库 - 分享文档赚钱的网站上搜索。

1、21.What is an experimental method? Experiments were first used in the natural sciences. All of us have had the experience of undertaking either a physical or chemical experiment in a laboratory. What have left in your memory by these experiments are tubes, chemicals, wires and other materials. What

2、is an experiment in a social science? I will answer this question first by a conceptual definition.32.Definition The experimental method is a scientific method that changes gradually conditions in plan under a certain control, and according to observation records and research data, determines the ca

3、usality between conditions and the phenomenon by measuring the accompanying phenomena and changes, then finds and summaries the objective laws of Second Language Acquisition. 43.The basic premise of an experimentnThe basic premise of an experiment is that all factors save one are held constant. nThe

4、 single factor is varied to see what effect it has on the phenomenon under investigation.nAs stated earlier, experiments have two criteria: there are at least two groups included in the study, a control group and an experimental group; the subjects are randomly assigned to one of those groups.55.Why

5、 do we have two groups? The purpose of having the two groups in the study is that if one group is treated in one manner, and another in a different manner and their post-treatment behavior differs, we can conclude that the behavior differs as a consequence of their different treatments. This can onl

6、y be concluded, of course, if the two groups are comparable to start with. 6 Random group assignment allows the researchers to assume that they have two truly comparable groups at the outset of the experiment. A further safeguard to assure group comparability (especially desirable when subject popul

7、ations are small) is to compare their performances on a pretest. If the experimental and control groups are equivalent and only the treatment they receive differs, then any post-treatment test differences can be attributed to the treatment itself.76.An example of an experiment Henrichsens factorial

8、design studying the effect of sandhi variation on the comprehensibility of English input. 1. sandhi variation: it refers to phonological modification such as contraction, assimilation. 2. the subjects of the experiment: native English-speaker, ESL learners with high English proficiency and low Engli

9、sh proficiency. 3. Two treatment conditions: the presence or absence of sandhi variation.81.The advantages of an experimental methodology2.The disadvantages and of an experimental methodology97.Summary Experimental studies are classified as pre-experimental, quasi-experimental and true experimental,

10、 and can be placed on continuum in terms of the degree of the researchers control. The pre-experimental studies are least controlled and the true-experimental studies, most controlled. The critical feature that separates these three types of experimental studies is the extent to which comparison gro

11、ups to look alike in all respects.10nThe best strategy to make the comparison groups similar is random assignment of subjects. True-experimental studies are characterized by randomization while randomization is absent in the other two types of experimental studies. Quasi-experimental ones involve na

12、turally occurring treatment groups that are fairly clear-cut. In this sense, although randomization is not present, the differences between the two groups can be identified, measured and eventually their effects can be extracted statistically. Such a statistical control may enable the treatment conditions to approximate the ideal experimental conditions. Pre-experimental studies are less controlled than quasi-experimental studies since there are no two identifiable groups to compare as such.11 结束语结束语