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Lecture 9

PSYCH 1X03 Lecture 9: Research Methods in Psychology

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McMaster University
Joe Kim

PSYCH 1X03 Research Methods in Psychology Module 1 & 2 Notes The Scientific Method 1. Construct a Theory • Collect a general set of ideas about the way the world works. 2. Generate a hypothesis • Form a testable statement guided by theories that make specific predic- tions about the relationship between variables. 3. Choose a research method • Determine the way in which the hypothesis will be tested 4. Collect data • Take measurements of the outcomes of the test 5. Analyze data • Understand the data and discover trends or relationships between the vari- ables 6. Report your findings • Publish articles in scholarly journals 7. Revise existing theories • Incorporate new information into our understanding of the world Theories that define our current world are sometimes challenged and revised to account for new findings. Every so often, there is a paradigm shift. E.g. in 1543 when Copernicus challenged the idea that the earth was at the center of the universe. Conducting an Experiment When testing a hypothesis: • Asingle experience might not be representative of all experiences • Personal experience might not be representative of others • Cannot be sure that the result is due to the variable you’re testing alone Control Groups • In the most basic of experiments, there will be two groups of participants: o An experimental group: the group that receives the manipulated indepen- dent variable o Acontrol group: the group that does not receive the manipulated indepen- dent variable o Ideally, the participants in the experimental and control groups should be as similar as possible o Therefore, any change in the dependent variable will only be due to the independent variable • Then the effect on the dependent variable is compared from both groups ▯1 Research Methods in Psychology PSYCH 1X03 Within-Subjects Design • Manipulating the independent variable within each participant to minimize the effect of external variables on the dependent measure • Problems: Time consuming, costly, practice effect Between Subjects Design • One groups acts as the control group and a different group acts as the experimen- tal group • Participants should be as similar as possible so the only difference is the manipu- lated variable • Any other differing traits are called confounding variables Selecting Subjects • If a very particular group of subjects is selected, conclusions can only be drawn on those particular people and not society as a whole • There is a difference between the sample and the population o Sample: The people we are collecting data about o Population: The people we are trying to learn more about • Sample should accurately represent the population so that the results can be gen- eralized • Choose a random sample: therefore reducing the change that the selected might be biased towards a specific group • RandomAssignment: Randomly assigning subjects to either the experimental or control group Subject Biases • The Placebo Effect should always be considered when designing an experiment where participants might know in advance the results of the experimental manipu- lation • This may result in Participant Bias • Away to counter the placebo effect is through Blinding • Experimenters may subconsciously promote the result that would support their hypothesis. This phenomenon is called Experimental Bias. o Can reduce experimental bias if the experimenter themselves does not know which group is experimental or control. This kind of study is called a Double-Blind Types of Descriptive Statistics • Pie graphs, Venn diagrams • Histogram ▯2 Research Methods in Psychology PSYCH 1X03 o The x-axis is divided into groups of values called bins. The y-axis mea- sures the number of values in the data set that fall into a given bin and is called the frequency. o Use this type of graph to show a Frequency Distribution, which is a smooth curved line that connects the peak of each bar on the graph • Normal Distributions result when enough data is collected and graphed. Exam- ples include IQ, height and test scores • Measures of Central Tendency o Tell us where a data set is centered o The most common method is the mean ▪ The mean is very susceptible to influence by outliers ▪ E.g. If you scores 89, 90, 90 and 91 on your first 4 tests but get a 30 on your 5 test; your average would be 78. But that’s not very representative of how you usually score. o Mode ▪ Only one of the stats that can be used for non-numeric
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