In an experiment monitoring productivity, for instance, it was hypothesized that additional lighting would increase productivity in factory workers. When workers were observed in additional lighting they were more productive, but only because they were being watched. If a control group was also observed with no additional lighting this effect would have been obvious.
To minimize the chances that an unintended variable influences the results, subjects must be assigned randomly to different treatment groups.
Random assignment is used to ensure that any preexisting differences among the subjects do not impact the experiment. Theoretically, the baseline of both the experimental and control groups will be the same before the experiment starts. Therefore, if there is a difference in the behavior of the two groups at the end of the experiment, the only reason would be the treatment given to the experimental group.
In this way, an experiment can prove a cause-and-effect connection between the independent and dependent variables. If the experimenter inadvertently interprets the information in a way that supports the hypothesis when other interpretations are possible, it is called the expectancy effect.
To counteract experimenter bias, the subjects can be kept uninformed on the intentions of the experiment, which is called single blinding. If the people collecting the information and the participants are kept uninformed, then it is called a double blind experiment. By using blinding, a researcher can eliminate the chances that they are inadvertently influencing the outcome of the experiment.
When running an experiment, a researcher will want to pay close attention to their design to avoid error that can be introduced by not balancing the conditions properly.
Consider the following example. You are running a study in which participants complete a task of pressing button A with their left hand if they see a green light and pressing button B with their right hand if they see a red light. You find support for your hypothesis that red stimuli are processed more quickly than green stimuli.
However, an alternative explanation is that people are faster to respond with their right hand simply because most people are right-handed. In this manner, you are anticipating and controlling for this extra source of error in your design.
One of the main strengths of experimental research is that it can often determine a cause and effect relationship between two variables. Another strength of experimental research is the ability to assign participants to different conditions through random assignment. Randomly assigning participants to conditions ensures that each participant is equally likely to be assigned to one condition or another, and that there are no differences between experimental groups.
Although experimental research can often answer the causality questions that are left unclear by correlational studies, this is not always the case. Sometimes experiments may not be possible or ethical. Consider the example of the studying the correlation between playing violent video games and aggressive behavior. It would be unethical to assign children to play lots of violent video games over a long period of time to see if it had an impact on their aggression.
If this is the case, the experiment is said to have poor external validity, meaning that the situation the participants were exposed to bears little resemblance to any real-life situation. Privacy Policy. Skip to main content. Researching Psychology.
Search for:. Types of Research Studies. Descriptive Research Descriptive research refers to the measurement of behaviors and attributes through observation rather than through experimental testing. Learning Objectives Explain when descriptive research is useful. Key Takeaways Key Points Descriptive studies do not test specific relationships between factors; however, they provide information about behaviors and attributes with the goal of reaching a better understanding of a given topic.
Descriptive research is a useful method of gathering information about rare phenomena that could not be reproduced in a laboratory or about subjects that are not well understood.
The most common type of descriptive research is the case study, which provides an in-depth analysis of a specific person, group, or phenomenon. While their findings cannot be generalized to the overall population, case studies can provide important information for future research. Key Terms case study : Research performed in detail on a single individual, group, incident, or community, as opposed to for example a sample of the whole population.
Correlational Research Correlational research can be used to see if two variables are related and to make predictions based on this relationship. Learning Objectives Interpret results using correlational statistics.
Key Takeaways Key Points There are some instances where experimental research is not an option for practical or ethical reasons. In these situations, correlational research can still be used to determine if two variables are related. Correlations can be used to make predictions about the likelihood of two variables occurring together. Correlation does not imply causation. Just because one factor correlates with another does not mean the first factor causes the other or that these are the only two factors involved in the relationship.
Only an experiment can establish cause and effect. Key Terms causation : The act by which an effect is produced; in psychological research, the assumption that one variable leads to another.
On a graph, a negative correlation will have a negative slope. On a graph, a positive correlation will have a positive slope. Experimental Research Experimental research tests a hypothesis and establishes causation by using independent and dependent variables in a controlled environment. Learning Objectives Compare the role of the independent and dependent variable in experimental design. Smoking cigarettes - Lung cancer. Many buffalo were killed. The streets were snow-packed and icy.
He broke his arm. The boss was busy. A basketball player was traveling. One of the main strengths of experimental research is that it can often determine a cause and effect relationship between two variables. By systematically manipulating and isolating the independent variable, the researcher can determine with confidence the independent variable's causal effect on the dependent variable. Causal research , also called explanatory research , is the investigation of research into cause-and-effect relationships.
To determine causality, it is important to observe variation in the variable assumed to cause the change in the other variable s , and then measure the changes in the other variable s.
Explanation: Repeated experiments which produce results consistent with a cause - effect relationship provide evidence to support the relation hypothesis.
Alternately an experiment can be used to disprove a cause - effect hypothesis. Causality is a difficult concept to define and even more difficult to prove. What are the three rules of causation? The first three criteria are generally considered as requirements for identifying a causal effect: 1 empirical association, 2 temporal priority of the indepen- dent variable, and 3 nonspuriousness.
You must establish these three to claim a causal relationship. What is an example of causation? Causality examples For example, there is a correlation between ice cream sales and the temperature, as you can see in the chart below.
Causal relationship is something that can be used by any company. However, we can't say that ice cream sales cause hot weather this would be a causation. What is the purpose of cause and effect? Cause and effect is a common way to organize information in a text. Paragraphs structured as cause and effect explain reasons why something happened or the effects of something.
The cause and effect text structure is generally used in expository and persuasive writing modes. What is the purpose of blocking in some experiments? What is the purpose of a placebo group in an experiment?
What is the goal of a matched pair design? What is the purpose of double blind experiments? What is statistical significance? Question ce. See all questions in Experimental Design.
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