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1、ExperimentalMethodandSExperimentalMethodandStatisticalReasoninginPtatisticalReasoninginPsychologysychology在心理学的实在心理学的实验方法和统计推理验方法和统计推理The Scientific MethodnThe four basic goals of psychology are to (1) describe, (2) explain, (3) predict, and (4) control or influence behavior and mental processes. nT
2、o achieve these goals, psychologists rely on the scientific method. The scientific method refers to a set of assumptions, attitudes, and procedures that guide researchers in creating questions to investigate, in generating evidence, and in drawing conclusions. The Scientific MethodnLike all scientis
3、ts, psychologists are guided by the basic scientific assumption that events are lawful. When this scientific assumption is applied to psychology, it means that psychologists assume that behavior and mental processes follow consistent patterns. nPsychologists are also guided by the assumption that ev
4、ents are explainable. Thus, psychologists assume that behavior and mental processes have a cause or causes that can be understood through careful, systematic study.The Scientific MethodnIn striving to discover and understand consistent patterns of behavior, psychologists are open-minded. They are wi
5、lling to consider new or alternative explanations of behavior and mental processes. nHowever, their open-minded attitude is tempered by a healthy sense of scientific skepticism. That is, psychologists critically evaluate the evidence for new findings, especially those that seem contrary to establish
6、ed knowledge. nAnd, in promoting new ideas and findings, psychologists are cautious in the claims they make.Empirical evidencenLike any science, psychology is based on empirical evidenceevidence that is the result of objective observation, measurement, and experimentation. nAs part of the overall pr
7、ocess of producing empirical evidence, psychologists follow the four basic steps of the scientific method. The Steps in the Scientific Methodn Formulate a specific question that can be tested.n Design a study to collect relevant data.n Analyze the data to arrive at conclusions.n Report the results.S
8、tep 1. Formulate a Hypothesis That Can Be Tested EmpiricallynOnce a researcher has identified a question or an issue to investigate, he or she must formulate a hypothesis that can be tested empirically. Formally, a hypothesis is a tentative statement that describes the relationship between two or mo
9、re variables. A hypothesis is often stated as a specific prediction that can be empirically tested, such as “psychological stress increases the likelihood of physical illness.”nThe variables contained in any given hypothesis are simply the factors that can vary, or change. These changes must be capa
10、ble of being observed, measured, and verified. The psychologist must provide an operational definition of each variable to be investigated. An operational definition defines the variable in terms of how it is to be measured, manipulated, or changed.Operational definitionsnOperational definitions are
11、 important because many of the concepts that psychologists investigatesuch as memory, happiness, or stresscan be measured in more than one way. nIn providing operational definitions of the variables in the study, the researcher spells out in very concrete and precise terms how the variables will be
12、manipulated or measured. In this way, other researchers can understand exactly how the variables were measured or manipulated in a particular study. Step 2. Design the Study and Collect the Data Descriptive methodsnDescriptive methods are research strategies for observing and describing behavior, in
13、cluding identifying the factors that seem to be associated with a particular phenomenon. Descriptive methods answer the who, what, where, and when kinds of questions about behavior. nWho engages in a particular behavior? What factors or events seem to be associated with the behavior? Where does the
14、behavior occur? When does the behavior occur? How often?The experimental methodnThe experimental method is used to show that one variable causes change in a second variable. In an experiment, the researcher deliberately varies one factor, then measures the changes produced in a second factor. nIdeal
15、ly, all experimental conditions are kept as constant as possible except for the factor that the researcher systematically varies. Then, if changes occur in the second factor, those changes can be attributed to the variations in the first factor.Step 3. Analyze the Data and Draw ConclusionsnOnce obse
16、rvations have been made and measurements have been collected, the raw data need to be summarized and analyzed. nResearchers use the methods of a branch of mathematics known as statistics to summarize, analyze, and draw conclusions about the data they have collected. nResearchers rely on statistics t
17、o determine whether their results support their hypotheses. They also use statistics to determine whether their findings are statistically significant. If a finding is statistically significantnIf a finding is statistically significant, it means that the results are not very likely to have occurred
18、by chance.n As a rule, statistically significant results confirm the hypothesis. Meta-analysisnA statistical technique called meta-analysis is increasingly being used in psychology to analyze the results of many research studies on a specific topic. nBasically, meta-analysis involves pooling the res
19、ults of several studies into a single analysis. By creating one large pool of data to be analyzed, metaanalysis can sometimes reveal overall trends that may not be evident in individual studies. nMeta-analysis is especially useful when a particular issue has generated a large number of studies, some
20、 of which have produced weak or contradictory results.Step 4. Report the Findings For advances to be made in any scientific discipline, researchers must publish or share their findings with other scientists. In addition to reporting their results, psychologists provide a detailed description of the
21、study itself, including the following:nWho participated in the studynHow participants were selectednHow variables were operationally definednWhat procedures or methods were usednHow the data were analyzednWhat the results seem to suggest The precise details of the studynDescribing the precise detail
22、s of the study makes it possible for other investigators to replicate, or repeat, the study. Replication is an important part of the scientific process. When a study is replicated and the same basic results are obtained again, scientific confidence that the results are accurate is increased. nConver
23、sely, if the replication of a study fails to produce the same basic findings, confidence in the original findings is reduced.Naturalistic ObservationnWhen psychologists systematically observe and record behaviors as they occur in their natural settings, they are using the descriptive method called n
24、aturalistic observation. nUsually, researchers engaged in naturalistic observation try to avoid being detected by their subjects, whether people or nonhuman animals. nThe basic goal of naturalistic observation is to detect the behavior patterns that exist naturallypatterns that might not be apparent
25、 in a laboratory or if the subjects knew they were being watched.A Case StudynA case study is an intensive, in-depth investigation of an individual or a small group of individuals. Case studies involve compiling a great deal of information, often from a variety of different sources, to construct a d
26、etailed picture of the person. nThe subject may be intensively interviewed, and his or her friends, family, and co-workers may be interviewed as well. Psychological records, medical records, and even school records may be examined. Other sources of information can include extensive psychological tes
27、ting and observations of the persons behavior. nClinical psychologists and other mental health specialists routinely use case studies to develop a complete profile of a psychotherapy client. Case studies are also used to investigate rare, unusual, or extreme conditions.SurveysnA direct way to find o
28、ut about the behavior, attitudes, and opinions of people is simply to ask them. In a survey, people respond to a structured set of questions about their experiences, beliefs, behaviors, or attitudes. nOne key advantage offered by survey research is that information can be gathered from a much larger
29、 group of people than is possible with other research methods. nTypically, surveys involve a carefully designed questionnaire in a paper-and-pencil format that is mailed to a select group of people. Computer-based or Internet-based surveys have become increasingly more common. And, surveys are still
30、 often conducted over the telephone or in person, with the interviewer recording the persons responses. SurveysnAs with paper-and-pencil surveys, the interviewer usually asks a structured set of questions in a predetermined order. Surveys are seldom administered to everyone within the particular gro
31、up or population under investigation. nInstead, researchers usually select a samplea segment of the larger group or population. Selecting a sample that is representative of the larger group is the key to getting accurate survey results. A representative sample very closely parallels, or matches, the
32、 larger group on relevant characteristics, such as age, sex, race, marital status, and educational level.IQ and Classification of Intelligence (DSM-IV and WAIS-R)130Very superiorThe Correlational StudynA correlational study examines how strongly two variables are related to, or associated with, each
33、 other. Correlations can be used to analyze the data gathered by any type of descriptive method. nThe participants also filled out a questionnaire on past delinquent behavior and completed tests designed to measure different personality characteristics. Finally, each respondents cumulative grade sho
34、uld point average. Once the data were collected from their survey participants, psychologists used statistical procedures to calculate a figure called a correlation coefficient. A correlation coefficient is a numerical indicator of the strength of the relationship between two factors. nA positive co
35、rrelation is one in which the two factors vary in the same direction. That is, the two factors increase or decrease together. For example, Anderson and Dill found that there was a positive correlation of .22 between the amount of time spent playing violent video games and aggressive personality char
36、acteristics. That is, as the amount of time spent playing violent video games increased, aggression scores on personality tests increased.nIn contrast, a negative correlation is one in which the two variables move in opposite directions: As one factor decreases, the other increases. For example, And
37、erson and Dill found that there was a negative correlation of .20 between the amount of time spent playing video games and academic achievement, as measured by cumulative college grade-point average. As the amount of time spent playing video games increased, college grade-point average decreased.The
38、 Correlational StudyExperimental method The experimental method is a research method used to demonstrate a cause-and-effect relationship between changes in one variable and the effect that is produced on another variable. Conducting an experiment involves deliberately varying one factor, which is ca
39、lled the independent variable. The researcher then measures the changes, if any, that are produced in a second factor, called the dependent variable. The dependent variable is so named because changes in it depend on variations in the independent variable. To the greatest degree possible, all other
40、conditions in the experiment are held constant. Thus, when the data are analyzed, any changes that occur in the dependent variable can be attributed to the deliberate variations of the independent variable. In this way, an experiment can demonstrate a cause-and-effect relationship between the indepe
41、ndent and dependent variables. Limitations of ExperimentsnThe strength of a well-designed experiment is that it can provide convincing evidence of a cause-and-effect relationship between the independent and dependent variables. nExperiments do have limitations, however. Because experiments are often
42、 conducted in highly controlled laboratory situations, they are frequently criticized for having little to do with actual behavior. That is, the artificial conditions of some experiments may produce results that do not generalize well, meaning that the results cannot be applied to real situations or
43、 to a more general population beyond the participants in the study. Limitations of ExperimentsnIn order to make experimental conditions less artificial, experiments are sometimes conducted in a natural setting rather than in a laboratory. nAnother limitation of the experimental method is that even when it is possible to create the conditions that the researchers want to study, it may be unethical to do so. The most spread personality testsnMinnesota Multiphasic Personality Inventory (MMPI)nEysenck Personality questionnaire (EPQ):nRorschach Inkblot testnThematic Apperception Test (TAT)结束结束
