2009年5月8日 星期五
內在效度
In scientific experimental settings, researchers often manipulate a variable (the independent variable) to see what effect it has on a second variable (the dependent variable).
For example, a researcher might, for different experimental groups, manipulate the dosage of a particular drug between groups to see what effect it has on health.
In this example, the researcher wants to make a causal inference, namely, that different doses of the drug may be held responsible for observed changes or differences. When the researcher may confidently attribute the observed changes or differences in the dependent variable to the independent variable, and when he can rule out other explanations (or rival hypotheses), then his causal inference is said to be internally valid.
內在效度:
當我們相信「差異」或「相關」的確存在時,接下來就可以問「差異是誰造成的?」是「獨變項」?還是另有其它因素呢?「內在效度」就是指實驗者對所操弄的「獨變項」對「依變項」造成影響的信心程度。當我們越有信心排除與獨變項無干的其它競爭因素,實驗的內在效度就越高。
Ceiling Effects(天花板效應)
天花板效應即「高限」效應。 在實驗設計時應避免出現。
當要求被試完成的任務過於容易,所有不同水平(數量)的自變量都獲得很好的結果,並且沒有什麼差別時,我們就說實驗中出現了天花板效應(高限)效應。
例如,測驗題目過於容易,造成考生得分普遍較高的現象,稱為天花板效應。
Weber's Fraction(韋伯分數)
WEBER'S LAW, in psychology, the name given to a principle first enunciated by the German scientist, Ernst Heinrich Weber (1795-1878), who became professor at Leipzig (of anatomy, 1818, of physiology, 1840).
He was-specially famous for his researches into aural and cutaneous sensations. His law, the purport of which is that the increase of stimulus necessary to produce an increase of sensation in any sense is not a fixed quantity but depends on the proportion which the increase bears to the immediately preceding stimulus, is the principal generalization of that branch of scientific investigation which has come to be known as psycho-physics
1834年由德國生理學家韋伯所提出:
人體感覺的科學性,稱為韋伯定律。(Weber's law)
他發現人類各種感覺,其差異閾限與標準刺激之間,成定比的關係。
韋伯定律公式如下:
JND/S=K
JND意指:可知覺的最小變化量(差異閾限)
S意指:標準刺激(標準刺激強度)
K則是:韋伯常數(韋伯分數)
以重量大小的判斷來為例,讓受試者閉上眼睛,用手比較兩個物體的重量。
假設一百公克為標準刺激,受試者在一百零三公克時,恰好能夠辨別這兩者差異,則三公克即為「差異閾限」。
假設標準刺激為兩百公克,受試者在兩百零六公克時,才能辨別兩者的差異。
由韋伯定律可以得到以下比值:
3/100=6/200=9/300=12/400=15/500=K
由上敘比值可知:重量一百公克時,只需加上三公克,即可感覺其差異,
兩百公克時,必須加上六公克才有感覺差異,依此類推。
Latin Square Design(拉丁方格設計)
A Latin square is an n × n table filled with n different symbols in such a way that each symbol occurs exactly once in each row and exactly once in each column.
拉丁方格是指:
兩種集區變數,處理水準數與兩個集區因子水準次數都相同。
則可將之處理安排在兩集區因子組合成的「方陣」中。
使每一列、每一行,各自出現一次處理水準。