Scientific Methods in Psychology Goals of the scientific method o Steps in scientific investigation Method 1 experimental methods o Vocabulary o Strengths and weaknesses Method 2 Descriptive Correlational Methods o Vocabulary o Strengths and weaknesses Statistics communication and clarity Goals o Measurement and description o Understanding causation and associations Prediction o Control and application Five steps in Scientific Investigation o Step one formulate a hypothesis o Step two design a study o Step three collect data o Step four analyze data and draw conclusions o Step five communicate findings Scientific Method 1 Experimental Method Vocabulary o Experiment manipulation of one variable under controlled conditions so that resulting changes in another variable can be observed A variable is anything that changes or differs So we can ask o Why does a variable change or differ o What happens to other variable when this variable changes or differs o Independent variable IV manipulated variable o Dependent variable DV measured variable the variable affected by manipulation How does X affect Y X independent variable and Y dependent variable o Operational definitions are used to clarify precisely what is meant by each variable in an experiment Designing an Experiment An Example o Hypothesis anxiety causes people to affiliate o Variable in this experiment Operational definitions IV anxiety tell experiment participants they will have to do a painful or a non painful task DV Affiliation ask subjects if they want to wait for the experiment alone or with others o The power of experimental control The only difference between groups is the independent variable Experimental group high anxiety Control group no anxiety o Differences in the DV between the group must be due to the manipulated IV High anxiety CAUSES a desire to affiliate Strengths and Weaknesses of Experimental Methods o Strengths o Weaknesses Conclusion about cause and effect can be drawn Artificial nature of experiments Ethical and practical issues Scientific Method 2 Descriptive Correlational Studies o Methods of data collection used when you cannot manipulate an IV Naturalistic observation Case studies Surveys Allow researchers to describe patterns of behavior and discover associations but cannot imply causation Descriptive statistics correlation o Correlated when two variable are related to each other o Correlation coefficient numerical index of degree of association Correlation expressed as a number between 1 00 and 1 00 Note can be positive or negative Numbers closer to 1 00 or 1 00 indicate stronger associations o Positive correlation when two variable change in the same direction o Negative correlation when two variable change in different direction Correlation examples positive or negative o Height and weight positive o Years of education and income positive o Years of education and time in jail negative o SAT scores and college achievement positive o Amount of crying and time being held negative o GPA and hours spent watching TV negative o Height and cravings for chocolate NONE