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Lecture 3

Unit 1 - Lecture 3 - Correlational Research & Experiments.docx

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Dalhousie University
PSYO 1011

PSYO 1011 Correlational Research & Experiments 1 Lecture 3: Correlational Research & Experiments September 17, 2009 Correlational Research: • Tries to quantify the relationships between naturally occurring variables • Asks about associations between naturally occurring variables • 3 Components o Researcher measures 1 variable (X) o Researcher measures 2 variable (Y) o Look for statistical relationship (X/Y) • How does correlational research differ from experimental research? o Correlational research measures but does not manipulate variables Correlation Coefficient: • Statistic that indicates the direction & strength of the association between 2 variables o Can be correlated positively or negatively o Range in value from -1.00 to +1.00  The closer the correlation is to -1 or +1, the stronger it is related • Positive Correlation o Higher scores on X are associated with high scores on Y o Positive slope o i.e.) People’s height is positively correlated with their height • Negative Correlation o Higher scores on X are associated with low scores on Y o Negative slope o i.e.) Depression is negatively correlated with the amount of monthly daylight • Zero Correlation o X & Y are not related statistically o Slope cannot be drawn o Zero correlation does not equal negative correlation o i.e.) Number of apples consumed per week and GPA Correlational Studies: • Advantages o Examines real-world variables o Addresses questions with ethical restraints  i.e.) Smoking has a correlation to cancer; while this is not directly related to smoking it links it o Can be used to make predictions  i.e.) Knowing score of one variable helps to predict the score of the other variable w/i certain limits • Disadvantages o Cannot draw conclusions about cause-effect Experiments: PSYO 1011 Correlational Research & Experiments 2 • Most direct method for testing explanations of why certain phenomena occur • 3 main characteristics o Manipulates one variable o Measures if this manipulation produces changes in a second variable o Attempts to control (but cannot) control extraneous factors that might influence the outcome of the experiment • RandomAssignment critical to experimental testing o However, groups still need to be comparable o Sample participants  Random assignment into experimental or control o Measure learning in both groups  Statistically compare performance of both groups Variables: • Independent Variable o Manipulated by the researcher  Cause o Two independent variables  Minimum 4 different groups • Dependent Variable o Measured by researcher  Effect o Depends on independent variable • Important to operationally define variables o i.e.) Listening to a tape of street sounds at 60dB for 30 minutes operationally defines the variable noise Experimental & Control Groups: • Experimental Group o Receives treatment or ‘active’level of independent variable o Common to have multiple experimental groups
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