Copyright © Allyn & Bacon 2007 Research Methods Copyright © Allyn & Bacon 2007

How Do Psychologists Develop New Knowledge? Psychologists, like researchers in all other sciences, use the scientific method to test their ideas empirically Copyright © Allyn & Bacon 2007

How Do Psychologists Develop New Knowledge? Empirical investigation – An approach to research that relies on sensory experience and observation as research data Scientific method – A five-step process for empirical investigation of a hypothesis under conditions designed to control biases and subjective judgments Copyright © Allyn & Bacon 2007 18

The Five Steps of the Scientific Method Developing a hypothesis Performing a controlled test Gathering objective data Analyzing the results Publishing, criticizing, and replicating the results Copyright © Allyn & Bacon 2007 19

The Five Steps of the Scientific Method Developing a hypothesis Hypothesis – A statement predicting the outcome of a scientific study Performing a controlled test Gathering objective data Operational definitions – Exact procedures used in establishing experimental conditions and measurement of results Analyzing the results Publishing, criticizing, and replicating the results Copyright © Allyn & Bacon 2007 19

The Five Steps of the Scientific Method Developing a hypothesis Independent variable – The variable manipulated by the experimenter Performing a controlled test Gathering objective data Random presentation – Using chance alone to determine the order in which the stimulus is presented Analyzing the results Publishing, criticizing, and replicating the results Copyright © Allyn & Bacon 2007 19

The Five Steps of the Scientific Method Developing a hypothesis Performing a controlled test Data – Information gathered by researcher and used to test a hypothesis Gathering objective data Analyzing the results Dependent variable – The measured outcome of a study; the responses of participants in a study Publishing, criticizing, and replicating the results Copyright © Allyn & Bacon 2007 19

The Five Steps of the Scientific Method Developing a hypothesis Performing a controlled test Gathering objective data Based on statistical analyses of results, the hypothesis is accepted or rejected Analyzing the results Publishing, criticizing, and replicating the results Copyright © Allyn & Bacon 2007 19

The Five Steps of the Scientific Method Developing a hypothesis Performing a controlled test Gathering objective data Analyzing the results Researchers must find out whether their work can withstand the scrutiny of the scientific community Publishing, criticizing, and replicating the results Copyright © Allyn & Bacon 2007 19

Types of Psychological Research In experiments, the researcher controls all the conditions and directly manipulates the conditions Non-experimental methods include: Correlational studies Surveys Naturalistic observation Longitudinal studies Cross-sectional studies Cohort-sequential studies Copyright © Allyn & Bacon 2007 24

Copyright © Allyn & Bacon 2007 Sources of Bias Sources of bias include: Personal bias Expectancy bias Bias could affect the way an experimenter designs a study, collects data, or interprets results Double blind studies attempt to control bias Researchers must also attempt to control confounding variables Copyright © Allyn & Bacon 2007 25

Copyright © Allyn & Bacon 2007 Ethics in Research Deception Debriefing Animal research Copyright © Allyn & Bacon 2007 27

Questions Science Cannot Answer The scientific method is not appropriate for answering questions that cannot be put to an objective, empirical test Ethics Morality Religious beliefs Preferences Copyright © Allyn & Bacon 2007

How Do We Make Sense of the Data? Researchers use statistics for two major purposes: (1) descriptively to characterize measurements made on groups or individuals and (2) inferentially to judge whether these measurements are the result of chance Copyright © Allyn & Bacon 2007

Copyright © Allyn & Bacon 2007 Class Survey Write down whether you agree or disagree with the following statements There is too much concern in the courts for the rights of criminals The death penalty should be abolished Wealthy people should pay a larger share of taxes then they do now Federal military spending should be increased Copyright © Allyn & Bacon 2007

Copyright © Allyn & Bacon 2007 Organizing the Data First results must be arranged in a summary chart known as a frequency distribution We can convert the data into a bar graph called a histogram Copyright © Allyn & Bacon 2007

Describing the Data With Descriptive Statistics Descriptive statistics include: The mean The median The mode The range The standard deviation The normal distribution Copyright © Allyn & Bacon 2007

Correlations: A relationship between Two Variables Correlation– A relationship between two variables, in which changes in one variable are reflected in changes in the other variable Correlation coefficient– A number between -1 and +1 expressing the degree of relationship between two variables Copyright © Allyn & Bacon 2007

Making Inferences with inferential statistics Inferential statistics are used to assess whether the results of a study are reliable or whether they might be simply the result of chance Sampling Random sample Representative sample Statistical significance Copyright © Allyn & Bacon 2007