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Unformatted text preview: PS101A
Monday September 20 & 27, 2010 1 What Are The Odds? Winning the lottery Killed by Lightning Killed by terrorists while travelling Dying in a Plane Crash Being in a Car Crash A Monkey typing "to be or not to be" A: under 1 in 200 B: 1in 200 to 1 in 1,000 C: 1 in 1,000 to 1 in 100,000 D: 1 in 100,000 to 1 in a million E: more than 1 in a million 2 What Are The Odds? http://www.cbc.ca/consumer/story/2009/11/09/fl http://science.discovery.com/videos/ 3 Psychology: Themes and Variations
Second Canadian Edition Appendix B
Statistical Methods Statistical Methods: Graphing Data Frequency distribution Histogram Frequency polygon 5 6 Descriptive Statistics Measures of Central Tendency Mean Median Mode Skewed Distributions Negative/Positive Measuring Variability Standard Deviation
7 8 9 10 11 The Normal Distribution Psychological tests Relative measures Standard deviation the unit of measure Conversion to percentile scores 12 13 14 Measuring Correlation Correlation coefficient Positive = direct relationship Negative = inverse relationship Magnitude: 0 to plus/minus 1 Scatter diagrams Correlation of determination 15 16 17 18 19 Hypothesis Testing Inferential statistics Sample Population Null hypothesis vs. research hypothesis Statistical significance 20 21 Psychology: Themes and Variations
Second Canadian Edition Chapter 2
The Research Enterprise in Psychology The Scientific Approach: A Search for Laws Basic assumption: events are governed by some lawful order Goals:
1. Measurement and description 2. Understanding and prediction 3. Application and control. 23 24 The Scientific Method: Terminology Operational definitions are used to clarify precisely what is meant by each variable Participants or subjects are the organisms whose behaviour is systematically observed in a study Data collection techniques allow for empirical observation and measurement. 25 The Scientific Method: Terminology Statistics are used to analyze data and decide whether hypotheses were supported Findings are shared through reports at scientific meetings and in scientific journals periodicals that publish technical and scholarly material Advantages of the scientific method: clarity of communication and relative intolerance of error Research methods: general strategies for conducting scientific studies.
26 Experimental Research: Looking for Causes Experiment = manipulation of one variable under controlled conditions so that resulting changes in another variable can be observed detection of causeandeffect relationships Independent variable (IV) = variable manipulated Dependent variable (DV) = variable affected by manipulation How does X affect Y? X= Independent Variable, and Y= Dependent Variable.
27 The Logic of the Scientific Method Experimental group subjects who receive some Experimental and Control Groups: special treatment in regard to the independent variable Control group similar subjects who do not receive the special treatment Logic: Extraneous and confounding variables. Two groups alike in all respects (random assignment) Manipulate independent variable for one group only Resulting differences in the two groups must be due to the independent variable 28 Experimental Designs: Variations Expose a single group to two different conditions Reduces extraneous variables Allows for study of interactions between variables Obtains a more complete picture of effect of the independent variable. Manipulate more than one independent variable Use more than one dependent variable 29 30 Strengths: Strengths and Weaknesses of Experimental Research
conclusions about causeandeffect can be drawn Weaknesses: artificial nature of experiments ethical and practical issues. 31 Methods used when a researcher cannot manipulate the variables under study
Naturalistic observation Case studies Surveys Descriptive/Correlational Methods: Looking for Links Allow researchers to describe patterns of behaviour and discover links or associations between variables but cannot imply causation. 32 33 Statistics and Research: Drawing Conclusions Statistics using mathematics to organize, summarize, and interpret numerical data Descriptive statistics: organizing and summarizing data Inferential statistics: interpreting data and drawing conclusions. 34 iClicker Question 9 students take a test Total of scores is 45 9 8 7 5 4 3 3 3 3 1. What is the mean? 9 5 3 45 4 a. b. c. d. e. 35 iClicker Question II 9 students take a test Total of scores is 45 9 8 7 5 4 3 3 3 3 1. What is the median? 9 5 3 45 4 a. b. c. d. e. 36 iClicker Question III 9 students take a test Total of scores is 45 9 8 7 5 4 3 3 3 3 1. What is the mode? 9 5 3 45 4 a. b. c. d. e. 37 Measures of Central Tendency Descriptive Statistics: Measures of central tendency = typical or average score in a distribution Mean: arithmetic average of scores Median: score falling in the exact centre Mode: most frequently occurring score Which most accurately depicts the typical?. 38 Descriptive Statistics: Variability Variability = how much scores vary from each other and from the mean Standard deviation = numerical depiction of variability High variability in data set = high standard deviation Low variability in data set = low standard deviation. 39 40 Descriptive Statistics: Correlation When two variables are related to each other, they are correlated. Correlation = numerical index of degree of relationship Correlation expressed as a number between 0 and 1 Can be positive or negative Numbers closer to 1 (+ or ) indicate stronger relationship.
41 42 Prediction, Not Causation Correlation: Higher correlation coefficients = increased ability to predict one variable based on the other SAT/ACT scores moderately correlated with first year college GPA 2 variables may be highly correlated, but not causally related alcohol problems and salary positively correlated does $$ cause drinking problems? the third variable problem.
43 iCLicker IV The more violent computer games Kenny plays the more violent he is with other kids in the schoolyard. A. B. C. D. Violent games cause Kenny to be violent. There is a positive correlation between game playing and violent behaviour. There is a negative correlation. There is no correlation.
44 45 Hypothesis testing: do observed findings support the hypotheses? Interpreting Data and Drawing Conclusions
Are findings real or due to chance? Inferential Statistics: Statistical significance = when the probability that the observed findings are due to chance is very low Very low = less than 5 chances in 100/ .05 level 46 Evaluating Research: Methodological Pitfalls Sampling bias Placebo effects Distortions in selfreport data:
Social desirability bias Response set Experimenter bias the doubleblind solution 47 48 iClicker World Domination A. B. C. D. The Heebies and the Geebies are running for control of the Earth. A survey of some of earth's inhabitants has the Heebies ahead 80% to 20% Who will win the election? The Heebies The Geebies We need more information Surveys are always wrong 49 WD II
The sample is representative The survey takes into account possible selfreport distortions The survey is considered accurate +/ 6% 19 times out of 20 The survey controlled for possible investigator bias What can we say?. 50 Ethics in Psychological Research: Do the Ends Justify the Means? The question of deception The question of animal research Controversy among psychologists and the public Ethical standards for research: the American Psychological Association and CPA Ensures both human and animal subjects are treated with dignity 51 ...
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- Fall '11