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Copyright © Allyn & Bacon 2007 Chapter 2: Research Methods

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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.

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

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Copyright © Allyn & Bacon 2007 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

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

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Copyright © Allyn & Bacon 2007 Operational Definition A definition that specifies the operations used to produce or measure something; a way to give it a numerical value. Example of an operational definition: Televised violence = the # of acts shown or described in which one person injures another.

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

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

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

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

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Copyright © Allyn & Bacon 2007 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

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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.

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Copyright © Allyn & Bacon 2007 Ethics in Research APA – American Psychological Association IRB – Institutional Review Board IACUC – Animal research (must be Appropriate, Beneficial, and Caring) Deception Debriefing

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

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Milgram Experiment

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Shock Generator Caution Amps On Intensity Resistance Amp Meter Slight Shock Moderate Shock Strong Shock Very Strong Shock Intense Shock Extreme Shock Danger XXX Milgram Experiment Two thirds of participants delivered the maximum 450 volts to the learner!

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Statistical Evaluation

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Descriptive Statistics: Statistical procedures used to describe characteristics and responses of groups of subjects. Mathematical summaries of results.

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Statistical Evaluation Frequency distribution: A summary chart, showing how frequently each of the various scores in a set of data occurs. RankDegree of agreementNumber 1Strongly agree25 2Agree somewhat35 3Not sure20 4Disagree somewhat15 5Strongly disagree5

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Statistical Evaluation Histogram: A bar graph depicting a frequency distribution. The height of the bars indicates the frequency of a group of scores.

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Measures of Central Tendency AVERAGES 1.Mean 2.Median 3.Mode

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Measures of Central Tendency Mean: Most commonly used to describe a set of data. Calculated by adding all the scores and dividing by the total number of scores. *What is the mean of the following numbers? 2, 4, 8, 9, 7, 3, 9

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Answer: 6

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Measures of Central Tendency Median: The middle score in a list of scores arranged from highest to lowest. *What is the median in this number list? 2, 3, 5, 7, 9 Answer: 5 Find the median: 11, 6, 9, 12, 4, 7, 2, 5

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Answer : 6.5

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Measures of Central Tendency Mode: The score that occurs the most frequently. *What is the mode of this distribution? 2, 3, 4, 6, 6, 7, 9

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Answer: 6

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Measures of Central Tendency What happens if there is more than mode??? Example: 2, 3, 4, 4, 5, 6, 7, 7, 8, 9

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Measures of Central Tendency The distribution is called BIMODAL. 2 modes = bimodal What is the mode? 2, 3, 4, 4, 5, 6, 7, 7, 8, 9 ANSWER: 4 AND 7

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Measures of Variation Variance: A measure of difference or spread (high or low). Range: Subtract the lowest score in the data set from the highest score and add 1. *If the highest quiz grade was 12 and the lowest quiz grade was 0, what is the range?

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Answer: 13

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Sampling

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Sampling Random sample: A sample group of subjects selected by chance (without bias). Representative sample: A sample that reflects the distribution of important variables in the larger population in which the researchers are interested.

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Correlation: The measure of a relationship between two variables. Correlation Coefficient: A mathematical estimate of the relationship between two variables. -1.0 to +1.0 0 = No Relationship

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Statistical Evaluation POSITIVE CORRELATION: + As one variable increases, the second variable increases. Example??? NEGATIVE CORRELATION: - As one variable increases, the second variable decreases. Example???

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ParticipantIncome Years of Education #1125,00019 #2100,00020 #340,00016 #435,00016 #541,00018 #629,00012 #735,00014 #824,00012 #950,00016 #1060,00017

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ParticipantGPA TV (hours per week) #13.114 #22.410 #32.020 #43.87 #52.225 #63.49 #72.915 #83.213 #93.74 #103.521

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Correlations Imagine reading four correlational studies with the following scores: -.3 -.8.4.7 Which study has the strongest results?

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Correlations -.8 is the strongest correlation (The negative sign means that its direction is negative)

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Statistical Evaluation Normal distribution: A symmetrical frequency of scores clustered around the mean. Bell-shaped curve

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Statistical Evaluation Standard Deviations: A measure of variability that describes an average distance of every score from the mean.

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Statistical Evaluation Inferential statistics: Used to assess whether the results of a study are reliable or whether they might be simply the result of chance.

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Statistical Significance p<.05 The probability that randomly generated results would resemble the observed results is less than 5% * The smaller the p value, the more impressive the results!

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Statistical Evaluation Statistically significant: Unlikely that the effects have arisen by chance.

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