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PSY 1950

PSY 1950. Delphine S. Courvoisier Harvard University TAs: Stephanie McMains Joseph McIntyre . Potential mistakes (instructor is Swiss). Temple, Bangkok : IT IS FORBIDDEN TO ENTER A WOMAN, EVEN A FOREIGNER, IF DRESSED AS A MAN.

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PSY 1950

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  1. PSY 1950 Delphine S. Courvoisier Harvard University TAs: Stephanie McMains Joseph McIntyre

  2. Potential mistakes (instructor is Swiss) • Temple, Bangkok : IT IS FORBIDDEN TO ENTER A WOMAN, EVEN A FOREIGNER, IF DRESSED AS A MAN. • Cemetery: PERSONS ARE PROHIBITED FROM PICKING FLOWERS FROM ANY BUT THEIR OWN GRAVES • Restaurant, Switzerland: OUR WINES LEAVE YOU NOTHING TO HOPE FOR. • Hotel, Japan: YOU ARE INVITED TO TAKE ADVANTAGE OF THE CHAMBERMAID. • Hotel, Zurich : BECAUSE OF THE IMPROPRIETY OF ENTERTAINING GUESTS OF THE OPPOSITE SEX IN THE BEDROOM, IT IS SUGGESTED THAT THE LOBBY BE USED FOR THIS PURPOSE. • Airline ticket office, Copenhagen: WE TAKE YOUR BAGS AND SEND THEM IN ALL DIRECTIONS. • Laundry, Rome : LADIES, LEAVE YOUR CLOTHES HERE AND SPEND THE AFTERNOON HAVING A GOOD TIME

  3. Information • Lectures (Mon and Wed 1-2:30, WJH 1305) • Ex-cathedra presentations • Small quizzes • Reading of recent articles • Writing of abstract and methods/results sections • Lab sessions (Tue 5-6:30,WJH 1305) • Learning how to input and analyze data

  4. Information and schedule • Course websitehttp://isites.harvard.edu/k89723 • Reading (compulsory) • Field, A. (2009). Discovering statistics using SPSS (3rd edition). London: Sage. • Reading (non compulsory; good short refresher) • Petrie, S., Sabin, C. (2009). Medical Statistics at a Glance (3rd edition). Sussex: Wiley.http://www.medstatsaag.com/

  5. Exam and grade • 20% participation • 20% exercises • 25% mid-term test • 35% final exam • Mid-term and final exam are an analysis of data given one week before the test, and questions asked on the analysis. • For an example, see folder exam on isites

  6. Lecture 1

  7. Why do you need statistics? • Duh!! To pass the exam • To understand the methods of data analysis used in scientific articles for (applied) psychologists and for researchershttp://www.jsur.org/v1n1p1 • To apply this knowledge to critical reading of scientific articles in your professional life (continued training) • To apply this knowledge to your own research

  8. Top 10 reasons to be a statistician • Deviation is considered normal • We feel complete and sufficient • We are 'mean' lovers • Statisticians do it discretely and continuously • We are right 95% of the time • We can legally comment on someone's posterior distribution • We may not be normal, but we are transformable • We never have to say we are certain • We are honestly significantly different • No one wants our jobs

  9. Structure of an article • Title • Summary (structured) • Body: • Introduction • Methods • Results • Discussion • References Why do the study How was the study done What was observed What does it mean

  10. Goal of statistical analysis • Describe data • Draw general conclusions about the world and its workings

  11. Question • You collect scores on the BDI (a 21-question multiple-choice self-report depression inventory) from a sample of children. In your research: • Depression is a discrete variable • Depression is a continuous variable • Depression is a ratio variable • Depression is an interval variable • It depends on how you think about depression • It depends on how you analyze the data

  12. Constructs and variables • Constructs are theoretical concepts • Variables are the proxy used to measure those constructs

  13. Question • You collect fMRI data from 10’000 individuals on a sustained attention task linked to ADHD, and plot the results (DV = % signal change) in a histogram. The distribution is very close to normal. These results: • provide strong evidence against a dichotomous view of ADHD. • could easily have arisen even if ADHD were a dichotomous phenomenon.

  14. Median vs. mean • Q: If you were to take 10,000 samples of n=25 from the below population and, for each sample, calculate its mean and median, how would the distributions of those two statistics vary from each other • http://onlinestatbook.com/stat_sim/sampling_dist/index.html

  15. Question These distributions differ in: Shape Dispersion Neither shape nor dispersion Both shape and dispersion

  16. Question These distributions differ in: Shape Dispersion Neither shape nor dispersion Both shape and dispersion

  17. Question • Using (http://onlinestatbook.com/stat_sim/sampling_dist/index.html) which of the following statements is true: • When sampling from normal distributions, the median is an unbiased statistic. • When sampling from skewed distributions, the median is a biased statistic. • both a and b

  18. Graphical representations • Histogram (sorted bar chart) • Box-plot • Scatterplot • Principles: • Have a clear visual message • Promote visual comparisons • Don’t cheat (axes, distortions, etc) • Show all the data • High ratio information/ink

  19. mode: 170 mean median Histogram Tendency to use “round” numbers

  20. outliers ¼ 3rd quartile ¼ Inter-quartile range median ¼ 1st quartile ¼ Smallest value Boxplot

  21. 4 equal areas p25 p50 p75 Percentiles and boxplots X

  22. Scatterplot, central tendency and dispersion

  23. Interaction plots

  24. How many statisticians does it take to change a light bulb? • With what degree of certainty do you need to know?

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