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LIVE INSPIRED LIVE TO LEARN Statistical Analyses: PB&J Peter J. Green Presented 3/14/2014; Missouri JSEHS Symposium Statistics • Importance for JESHS – Difference between interesting and stellar – Based on relatively simple math (algebra) – Tools exist for computation – Basic understanding is possible MARYVILLE UNIVERSITY 2 The PB&J • Descriptive Statistics • • • • P-values Correlations T-tests (2 types) ANOVA MARYVILLE UNIVERSITY 3 Descriptive Statistics • Importance of Mean, Standard Deviation • MUST be present MARYVILLE UNIVERSITY 4 Correlation • Measure of association between pairs of variables • Range: -1.00 to +1.00 – Closer to +1.00, stronger the relationship – Closer to 0.00, weaker the relationship – Real world: .30 is a solid correlation MARYVILLE UNIVERSITY 5 Correlation • Issues – Linear Relationships Only – Influence of Outliers • Both identifiable by a scatterplot – Impact of sample size • Need 20+ to find significance – Determination of p-value MARYVILLE UNIVERSITY 6 Correlation One individual who is extreme on one or both variables can drastically alter the r value. Eliminate the dot on the upper right, the correlation is – 0.14, but with that data point is + 0.39. (Nolan & Heinzen, 2012). MARYVILLE UNIVERSITY 7 T-tests • Comparison of 2 means – Technically the difference between 2 means/variability – Larger samples are better (+20) – Impact of outliers MARYVILLE UNIVERSITY 8 T-tests • Independent Samples T-tests – Data from 2 separate groups • Dependent Samples (Paired) T-tests – 2 pieces of data from the same group • Pre versus post • 2 attitudes, etc. • t (df) = 4.12, p < .05 MARYVILLE UNIVERSITY 9 Analysis of Variance • ANVOA – Comparison of 3 or more means – F (df, df) = 12.32, p < .05 MARYVILLE UNIVERSITY 10 How Do I… • Pearson Correlation – Excel (or Google Spreadsheet) • http://www.gifted.uconn.edu/siegle/research/correlation/ex cel.htm – SPSS • http://www.youtube.com/watch?v=VOI5IlHfZVE – Contains statistical jargon, but gets the point across; need to have data input first. MARYVILLE UNIVERSITY 11 How Do I…. • T-tests – Excel • https://www.usciences.edu/biology/bs130/statistics%20for %20biology-t%20test.html – – – – Tails: safest to assume 2 Type: 1=matched pair; 2=unmatched pair; 3=unequal variance Does not return a t-value! Must then use T.INV » OR use Data Analysis – much more information!!! – SPSS • http://www.mhhe.com/socscience/psychology/runyon/spss/ ttest.html MARYVILLE UNIVERSITY 12 How Do I… • T-tests – SPSS • http://www.mhhe.com/socscience/psychology/runyon/ spss/ttest.html – Format of data is very different! » Paired = 2 data points in the same row » Independent = needs a grouping variable; all data will be in the same column; one data point per row MARYVILLE UNIVERSITY 13 How Do I… • ANOVA – Excel: – Single Factor – http://www.excel-easy.com/examples/anova.html – Really nice website for using Excel. » Warning: Generally recognized that results will not be as accurate as SPSS or SAS etc. – Beyond this point we are no longer dealing with PB&J, but are into gourmet breads and hand ground organic peanuts… MARYVILLE UNIVERSITY 14 How Do I… • ANOVA – SPSS: – One way (Single Factor) – Host of good YouTube videos… – http://www.youtube.com/watch?v=_btBuD3LIsM – Again, moving beyond isn’t PB&J. MARYVILLE UNIVERSITY 15 PB&J • Questions? MARYVILLE UNIVERSITY 16