Like other sciences, psychology utilizes the scientific method and bases conclusions upon empirical evidence. When conducting an experiment, it is important to follow the seven basic steps of the scientific method:
Investigate a commonly held belief. Folk knowledge is a good source of questions that can serve as the basis for psychological research. For example, many people believe that staying up all night to cram for a big exam can actually hurt test performance. You could conduct a study to compare the test scores of students who stayed up all night with the scores of students who got a full night’s sleep prior to the exam.Review psychology literature. Published studies are a great source of unanswered research questions. In many cases, the authors will even note the need for further research. Find a published study that you find intriguing, and then come up with some questions that require further exploration.Think about everyday problems. There are many practical applications for psychology research. Explore various problems that you or others face each day, and then consider how you could research potential solutions. For example, you might investigate different memorization strategies to determine which methods are most effective.
In this example, you might define sleep deprivation as getting less than seven hours of sleep at night. You might define driving performance as how well a participant does on a driving test. What is the purpose of operationally defining variables? The main purpose is control. By understanding what you are measuring, you can control for it by holding the variable constant between all of the groups or manipulating it as an independent variable. In order to determine if the results of the study are significant, it is essential to also have a null hypothesis. The null hypothesis is the prediction that one variable will have no association to the other variable. In other words, the null hypothesis assumes that there will be no difference in the effects of the two treatments in our experimental and control groups. The null hypothesis is assumed to be valid unless contradicted by the results. The experimenters can either reject the null hypothesis in favor of the alternative hypothesis or not reject the null hypothesis. Reading previous research helps you gain a better understanding of what you will encounter during your own experiment. Understanding the background of your topic provides a better basis for your own hypothesis. After conducting a thorough review of the literature, you might choose to alter your own hypothesis. Background research also allows you to explain why you chose to investigate your particular hypothesis and articulate why the topic merits further exploration.
Pre-experimental design: A single group of participants is studied, and there is no comparison between a treatment group and a control group. Examples of pre-experimental designs include case studies (one group is given a treatment and the results are measured) and pre-test/post-test studies (one group is tested, given a treatment and then retested). Quasi-experimental design: This type of experimental design does include a control group, but does not include randomization. True experimental design: A true experimental design includes both of the elements that pre-experimental designs and quasi-experimental designs lack—control groups and random assignment to groups.
For example, in our hypothetical study on the effects of sleep deprivation on driving performance, the driving test must be administered to each participant in the same way. The driving course must be the same, the obstacles faced must be the same, and the time given must be the same. When choosing subjects, there are a number of different techniques you can use.
Simple random sample: Participants are randomly selected from a group.Stratified random sample: Participants must be randomly selected from different subsets of the population. These subsets might include characteristics such as geographic location, age, sex, race, or socioeconomic status.
First, you need to be sure that your testing procedures are ethical. Generally, you will need to gain permission to conduct any type of testing with human participants by submitting the details of your experiment to your school’s Institutional Review Board (IRB), sometimes referred to as the Human Subjects Committee. After you have gained approval from your institution’s IRB, you will need to present informed consent forms to each of your participants. This form offers information on the study, the data that will be gathered, and how the results will be used. The form also gives participants the option to withdraw from the study at any point in time. Once this step has been completed, you can begin administering your testing procedures and collecting the data. The types of statistical methods you use to analyze your data depend largely on the type of data that you collected. If you are using a random sample of a larger population, you will need to utilize inferential statistics. These statistical methods make inferences about how the results relate to the population at large. Because you are making inferences based upon a sample, it has to be assumed that there will be a certain margin of error. In your case, it is likely that your class instructor will expect a formal write-up of your experiment in the same format required in a professional journal article or lab report:
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