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INF397C Introduction to Research in Information Studies Spring, 2009 Day 13. Correlation. With correlation, we return to DESCRIPTIVE statistics. (This is counterintuitive. To me.) (Well, it’s BOTH descriptive and inferential.)
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INF397CIntroduction to Research in Information StudiesSpring, 2009Day 13
Correlation • With correlation, we return to DESCRIPTIVE statistics. (This is counterintuitive. To me.) (Well, it’s BOTH descriptive and inferential.) • We are describing the strength and direction of the relationship between two variables. • And how much one variable predicts the other.
Correlation • Formula – • Hinton, p. 259, or • S, Z, & Z, p. 393 • Two key points: • How much predictability does one variable provide, for another. • NOT causation.
Correlation (cont’d.) • Go to the McGraw-Hill statistics primer http://highered.mcgraw-hill.com/sites/0072494468/student_view0/statistics_primer.html and click on “Correlational Statistics.” Read the three sub-sections. I will NOT ask you to calculate a correlation, but I want you to understand the concepts surrounding it.
Chi-square • Hinton, p. 247
Chi square test • Let’s work an example. • Just know that you use the chi square test when you have FREQUENCY data.
Let’s talk about the final • Here’s what you’ve read: • Huff (How to lie with statistics) • Dethier (To know a fly) • Hinton: Ch. 1 – 15, 20 • S, Z, & Z: Ch. 1-8, 10-13 • Several other articles
For the final, EMPHASIZE… • Descriptive stat • Measures of central tendency, dispersion • Z scores • Probability • Frequency distributions, tables, graphs • Correlation (interpret, not calculate) • Inferential stat • Hypothesis testing • Standard error of the mean • t test (calculate one, for one sample; interpret others) • Confidence intervals (interpret, not calculate) • Chi square (interpret, not calculate) • ANOVA – interpret summary table • Type I and II errors
Emphasize . . . • Experimental design • IV, DV, controls, confounds, counterbalancing • Repeated measures, Independent groups • Sampling • Operational definitions • Individual differences variable • Ethics of human study • Possible sources of bias and error variance and how to minimize/eliminate • Qualitative methods • Per Rice Lively, Gracy • Survey generation (from SZZ, Ch. 5)
De-emphasize • Complicated probability calculations • APA ethical standard (S,Z, & Z, Ch. 3) • Content analysis (SZZ, Ch. 6) • Calculating an ANOVA. • Nonequivalent control group design (SZZ, Ch. 11) (Indeed, de-emphasize all Ch. 11) • Hinton, Ch. 12