Still another possible explanation for the observed correlation is that it has been produced by the presence of a common-causal variable also known as a third variable. A common-causal variable A variable that is not part of the research hypothesis but that causes both the predictor and the outcome variable and thus produces the observed correlation between them.
Parents who use a harsh and punitive discipline style may produce children who both like to watch violent television and who behave aggressively in comparison to children whose parents use less harsh discipline:. In this case, television viewing and aggressive play would be positively correlated as indicated by the curved arrow between them , even though neither one caused the other but they were both caused by the discipline style of the parents the straight arrows.
When the predictor and outcome variables are both caused by a common-causal variable, the observed relationship between them is said to be spurious.
If effects of the common-causal variable were taken away, or controlled for, the relationship between the predictor and outcome variables would disappear.
Since it is not possible to measure every variable that could cause both the predictor and outcome variables, the existence of an unknown common-causal variable is always a possibility. For this reason, we are left with the basic limitation of correlational research: Correlation does not demonstrate causation. It is important that when you read about correlational research projects, you keep in mind the possibility of spurious relationships, and be sure to interpret the findings appropriately.
Although correlational research is sometimes reported as demonstrating causality without any mention being made of the possibility of reverse causation or common-causal variables, informed consumers of research, like you, are aware of these interpretational problems. In sum, correlational research designs have both strengths and limitations. One strength is that they can be used when experimental research is not possible because the predictor variables cannot be manipulated. Correlational designs also have the advantage of allowing the researcher to study behavior as it occurs in everyday life.
And we can also use correlational designs to make predictions—for instance, to predict from the scores on their battery of tests the success of job trainees during a training session. But we cannot use such correlational information to determine whether the training caused better job performance. For that, researchers rely on experiments. The goal of experimental research design is to provide more definitive conclusions about the causal relationships among the variables in the research hypothesis than is available from correlational designs.
In an experimental research design, the variables of interest are called the independent variable or variables and the dependent variable. The independent variable In and experiment, the causing variable that is created manipulated by the experimenter. The dependent variable In an experiment, the measured variable that is expected to be influenced by the experimental manipulation. The research hypothesis suggests that the manipulated independent variable or variables will cause changes in the measured dependent variables.
We can diagram the research hypothesis by using an arrow that points in one direction. This demonstrates the expected direction of causality:. Consider an experiment conducted by Anderson and Dill Video games and aggressive thoughts, feelings, and behavior in the laboratory and in life. Journal of Personality and Social Psychology, 78 4 , — The study was designed to test the hypothesis that viewing violent video games would increase aggressive behavior.
In this research, male and female undergraduates from Iowa State University were given a chance to play with either a violent video game Wolfenstein 3D or a nonviolent video game Myst.
During the experimental session, the participants played their assigned video games for 15 minutes. Then, after the play, each participant played a competitive game with an opponent in which the participant could deliver blasts of white noise through the earphones of the opponent.
The operational definition of the dependent variable aggressive behavior was the level and duration of noise delivered to the opponent. The design of the experiment is shown in Figure 2.
Two advantages of the experimental research design are 1 the assurance that the independent variable also known as the experimental manipulation occurs prior to the measured dependent variable, and 2 the creation of initial equivalence between the conditions of the experiment in this case by using random assignment to conditions.
Experimental designs have two very nice features. For one, they guarantee that the independent variable occurs prior to the measurement of the dependent variable. This eliminates the possibility of reverse causation. Second, the influence of common-causal variables is controlled, and thus eliminated, by creating initial equivalence among the participants in each of the experimental conditions before the manipulation occurs. The most common method of creating equivalence among the experimental conditions is through random assignment to conditions A procedure used in experimental research designs in which the condition that each participant is assigned to is determined through a random process.
Anderson and Dill first randomly assigned about participants to each of their two groups Group A and Group B. Because they used random assignment to conditions, they could be confident that, before the experimental manipulation occurred, the students in Group A were, on average, equivalent to the students in Group B on every possible variable, including variables that are likely to be related to aggression, such as parental discipline style, peer relationships, hormone levels, diet—and in fact everything else.
Then, after they had created initial equivalence, Anderson and Dill created the experimental manipulation—they had the participants in Group A play the violent game and the participants in Group B play the nonviolent game. Then they compared the dependent variable the white noise blasts between the two groups, finding that the students who had viewed the violent video game gave significantly longer noise blasts than did the students who had played the nonviolent game.
Anderson and Dill had from the outset created initial equivalence between the groups. This initial equivalence allowed them to observe differences in the white noise levels between the two groups after the experimental manipulation, leading to the conclusion that it was the independent variable and not some other variable that caused these differences.
The idea is that the only thing that was different between the students in the two groups was the video game they had played. Despite the advantage of determining causation, experiments do have limitations. One is that they are often conducted in laboratory situations rather than in the everyday lives of people. Therefore, we do not know whether results that we find in a laboratory setting will necessarily hold up in everyday life.
Second, and more important, is that some of the most interesting and key social variables cannot be experimentally manipulated. If we want to study the influence of the size of a mob on the destructiveness of its behavior, or to compare the personality characteristics of people who join suicide cults with those of people who do not join such cults, these relationships must be assessed using correlational designs, because it is simply not possible to experimentally manipulate these variables.
Creative Commons supports free culture from music to education. Their licenses helped make this book available to you. Help a Public School. Explain the goals of descriptive research and the statistical techniques used to interpret it. Summarize the uses of correlational research and describe why correlational research cannot be used to infer causality. Review the procedures of experimental research and explain how it can be used to draw causal inferences.
Allows the development of questions for further study. Does not assess relationships among variables. May be unethical if participants do not know they are being observed. Correlational To assess the relationships between and among two or more variables Allows testing of expected relationships between and among variables and the making of predictions. Can assess these relationships in everyday life events.
Cannot be used to draw inferences about the causal relationships between and among the variables. Experimental To assess the causal impact of one or more experimental manipulations on a dependent variable Allows drawing of conclusions about the causal relationships among variables.
Cannot experimentally manipulate many important variables. May be expensive and time consuming. There are three major research designs used by psychologists, and each has its own advantages and disadvantages. Assessing the Current State of Affairs Descriptive research is designed to create a snapshot of the current thoughts, feelings, or behavior of individuals. Original work published Figure 2. Olive Coding categories Episode Proximity Contact Resistance Avoidance Mother and baby play alone 1 1 1 1 Mother puts baby down 4 1 1 1 Stranger enters room 1 2 3 1 Mother leaves room; stranger plays with baby 1 3 1 1 Mother reenters, greets and may comfort baby, then leaves again 4 2 1 2 Stranger tries to play with baby 1 3 1 1 Mother reenters and picks up baby 6 6 1 2 Coding categories explained Proximity The baby moves toward, grasps, or climbs on the adult.
Maintaining contact The baby resists being put down by the adult by crying or trying to climb back up. Avoidance The baby turns away or moves away from the adult. Each of the four coding categories is scored by the coder from 1 the baby makes no effort to engage in the behavior to 7 the baby makes a significant effort to engage in the behavior. For instance, the experiment could be performed only on women, or on mixed groups with equal numbers of each sex in them, to eliminate the possibility of biased results from one gender having better average memory than the other.
Steps must be taken to make sure that there is no experimenter bias. Two common forms of bias are demand characteristics and expectancy effects. If a researcher expects certain results from an experiment and influences the subjects response this is called demand characteristics.
If the experimenter inadvertently interprets the information to be as expected in his hypothesis it is called expectancy effect. To counteract experimenter bias the subjects can be kept uninformed on the intentions of the experiment, which is called single blind. If the people collecting the information and the subjects giving it are kept uninformed then it is called a double blind experiment.
The experiment should also be reported so that other researchers can repeat it. If an experiment isn't repeatable it will not hold much weight in the scientific community.
To help an experiment be repeatable the researcher should have the variables be measureable, this is called being empirical. Whether researching humans or animals the experiment should be ethical. When humans are the subjects they should be informed of what the study is, consent to being in it, be debriefed afterwards, and their information should also be kept confidential. Researchers study organisms in their natural environments or habitats without trying to manipulate or control anything.
In this method, the researcher observes the behavior under study in its natural setting while attempting to avoid influencing or controlling it. The observations are done in a naturalistic setting without any preparation or participation of the researcher. Therefore, the behavior is observed in public places, streets, homes, and schools. Observing people from other cultures response in the same setting is a way to provide information for cross-cultural research.
This method includes tests , questionnaires , and interviews. All of which do the same thing, give the subject a stimuli, i. The advantage of using these is the ability to inexpensively and rapidly collect vast amounts of data. This allows a psychologist to compare one person, or a group of peoples results to thousands of others. The disadvantage is that they are not always telling what the subject's response is but what the subject says is the response. Once the information is gathered it has to be put into some kind of form, usually numerical.
Statistics deals with the collection, analysis, interpretation, and presentation of numerical data. The goal of statistics is to summarize the data and let descriptions or inferences be made. Inferences are used when making predictions of the relationships of variables. Descriptions are concise displays, using statistical symbols ,of the information in frequency distributions, measures of central tendency , or measures of variability.
There are agreed upon standard symbols used in statistical displays. These symbols can be used by themselves or in equations. A frequency distribution is obtained by taking the score and splitting them into subgroups. The subgroups are then put on either a histogram bar graph or a frequency polygram line graph. When a frequency distribution has most of the scores on one side of the graph it is considered skewed. If it has most of the scores in the middle with equal amounts on both sides it is considered symmetrical.
In measures of central tendency there is one number that is used to represent a group of numbers. This number is either the mean , median , or the mode. Variability is concerned with the dispersement of the scores, called variability i.
Range and standard deviation are the measures most commonly used. To find the range just subtract the number of the lowest score from the number of the highest score. They do not make accurate predictions, and they do not determine cause and effect. There are three main types of descriptive methods: This article will briefly describe each of these methods, their advantages, and their drawbacks. This may help you better understand research findings, whether reported in the mainstream media, or when reading a research study on your own.
With the observational method sometimes referred to as field observation animal and human behavior is closely observed. There are two main categories of the observational method — naturalistic observation and laboratory observation. The biggest advantage of the naturalistic method of research is that researchers view participants in their natural environments. This leads to greater ecological validity than laboratory observation, proponents say.
Proponents of laboratory observation often suggest that due to more control in the laboratory, the results found when using laboratory observation are more meaningful than those obtained with naturalistic observation. Laboratory observations are usually less time-consuming and cheaper than naturalistic observations. Of course, both naturalistic and laboratory observation are important in regard to the advancement of scientific knowledge. Case study research involves an in-depth study of an individual or group of indviduals.
Case studies often lead to testable hypotheses and allow us to study rare phenomena. Case studies should not be used to determine cause and effect, and they have limited use for making accurate predictions.
Descriptive research methods are pretty much as they sound -- they describe situations. They do not make accurate predictions, and they do not determine cause and effect. There are three main types of descriptive methods: observational methods, case-study methods and survey methods.
Descriptive Research Methods in Psychology Georgia Institute of Technology About this course: This is a five-section course as part of a two-course sequence in Research Methods in Psychology.
In psychology, techniques used to describe behavior include case studies, surveys, naturalistic observation, interviews, and psychological tests. Case studies. A case study is a method of obtaining information from the detailed observation of . Descriptive or Correlational Research Methods Case studies, surveys, naturalistic observation, and laboratory observation are examples of descriptive or correlational research methods. Using these methods, researchers can describe different events, experiences, or behaviors and look for links between them.
This is the essence of descriptive research in the field of psychology, and is the focus of this lesson. Definition As the name implies, descriptive research methods are used when the researcher wants to describe specific behavior as it occurs in the environment. Descriptive research seeks to depict what already exists in a group or population. An example of this type of research would be an opinion poll to determine which presidential candidate people plan to vote for in the next election.