reading2-研究类型

Types of Studies in Psychological Research

There are three main types of studies in psychological research: descriptive, correlational, and experimental. In descriptive and correlational designs, researchers examine behavior as it naturally occurs. These types of studies are useful for describing and predicting behavior, but they do not allow researchers to assess causality. Correlational designs have limitations, including directionality problems (knowing whether variable A caused B or the reverse) and the third variable problem, (the possibility that a third variable is responsible for variables A and B). In an experiment, a researcher manipulates the independent variable to study how it affects the dependent variable. An experiment allows a researcher to establish a causal relationship between the independent and dependent variable and to avoid the directionality problem when trying to understand how one variable might affect another. An experiment gives the researcher the greatest control, so that the only thing that changes is the independent variable. If the goals is to conclude that changes in one variable caused changes in another variable, the researcher must assign participants at random to different groups to make the groups as equal as possible (on average) on all variables except the one being studied. The researcher wants to know about a population, but because it is usually impossible for everyone in the population to be a research participant, the researcher uses a representative sample of the population and then generalizes the findings to the population. Random sampling, in which everyone in the population has an equal chance of being a research participant, is the best way to sample, but since this is usually not possible, most researchers use a convenience sample. Among the most important factors in whether the results from a particular sample can be generalized back to the population is sample size. In general, large samples provide more accurate results than small ones.

心理学研究的类型

心理学研究的类型主要有三种：描述、相关和实验研究。在实验和相关设计中，研究者研究自然发生的行为。这两种类型的研究对描述和预测行为是很有用的，但是他们无法让研究者对因果关系进行评价。相关设计的局限性包括方向性问题（知道是否变量A导致了变量B，反之亦言）和第三变量问题（第三个变量同时导致了变量A和变量B）。在实验研究中，研究者操纵自变量来研究自变量是如何影响因变量的。实验研究允许研究者在自变量和因变量之间建立因果关系，并使得研究者在试图了解一个变量是如何影响另一个变量时避开了方向性的问题。实验研究让研究者有最大的操控权，因为只有自变量才是可变的。如果是为了得出一个变量的变化引起了另一个变量的变化这样的结论，研究者必须把被试随机地分配到不同的组使得每个组在除了自变量以外的所有变量上都是相等的。研究者想知道总体的情况，但是因为通常不太可能让总体中的每个人都成为被试，所以研究者用能够代表总体的样本，并将结果推论到总体。随机取样，即让总体中的每个人都有相等的机会成为研究对象，是最佳的取样方法，但是由于这通常不太可能，所以大多数的研究者都用便利样本。样本大小是影响从特定样本所得结论能否推论到总体的最重要的原因之一。总之，从大样本所得结论比从小样本所得结论更准确。

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