Here it is…. …Your Super Duper Faster than Ever Pooper Scooper Review of Statistics and Data Analysis!

Types of Data  Nominal – identifies categories  e.g. gender, color, yes/no  Ordinal – identifies rank order  e.g. class rank  Interval – falls in a number line with an absolute zero (which means “the absence of”)  e.g. height and weight  Ratio – falls in a number line, but 0 is just another number  e.g. temperature

Figure 1.10 A skewed distribution Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers Descriptive Statistics  Measures of Central Tendency  mean, median, mode (Which is easily skewed?)  If the 3 are =, you have bell curve. If not, a skew.  Positive skew = scores pull mean higher  Negative skew = scores pull mean lower  Question: Which skew is this an example of?

Measures of Variation  Range (crude estimate)  Standard Deviation – the higher the number, the greater variability of scores Table 1.4 Source: Myers, Psychology, Eighth Edition, Copyright © 2007 by Worth Publishers

Inferential Statistics  In order to generalize from samples…:  Use representative samples  Use larger sample sizes  Observations with low variability are more reliable  Statistical Significance – the likelihood that the difference in samples’ means is due to chance  Goal is a significance of.05 or less  In other words, it is only 5% likely the difference is due to chance (or 95% likely the difference may be attributed to the Independent Variable)

Figure 1.3 Scatterplots, showing patterns of correlation Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers Correlation Correlation Coefficient – a statistical measure of the strength of the relationship between variables e.g (number indicates strength, sign indicates direction of correlation) Ranges from to Positive Correlation – two factors increase or decrease together (“DIRECT” correlation) Negative Correlation – one factor increases as the other decreases (“INVERSE” correlation)

Figure 1.5 Three possible cause-effect relationships Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers Correlation does NOT equal Causation!  People with low self-esteem are more likely to report depression. Why?

Experimental Design  Between-subjects design:  Compares one group of people to another  Most common method  Efficient method, but individual differences of the people may influence the results  Within-subjects design:  Compares participants to themselves  Pre-test  Ind. Variable  Post-test  Less efficient and more time-consuming, but resistant to the possible effects of individual differences

For More Practice…  Use the PsychSim Tutorials on the textbook website! textbook website textbook website  Click on “PsychSim Tutorials” and then Click on Chapter 1, “Descriptive Statistics” and/or “Correlation Analysis”