Lesson 10 rm psych stats & graphs 2013

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Lesson 10 rm psych stats & graphs 2013

  1. 1. Research Methodsin PsychologyStatisticsLesson 10:Saturday, 20 April 13
  2. 2. Lesson 9EXAM QUESTIONTaken from VCAA 2011 Mid Year ExamSaturday, 20 April 13
  3. 3. TextSaturday, 20 April 13
  4. 4. Lesson 10: Statistics* Define descriptive statistics * Define inferential statistics * Describe the types of statistics in Psychology:- calculate measures of central tendency including mean,median and mode-interpret p-values and draw conclusions-evaluate research in terms of generalizing the findings tothe population What you need to know and be able to doSaturday, 20 April 13
  5. 5. Generalising ResultsTo be able to generalise results, the following criteriamust be met:The results show statistical significance (p<0.05)All sampling procedures were appropriateAll experimental procedures were appropriateAll measures were validAll possible confounding variables were controlled.Saturday, 20 April 13
  6. 6. Types of StatisticsIn psychology there are two types ofstatistics1) Descriptive Statistics, show results2) Inferential Statistics, explains results inrelation to hypotheses.Saturday, 20 April 13
  7. 7. Descriptive statisticsTest A -1,7,22,66,4,3,55,44,5,6,78,789,23,1,23,Test B -67,43,67,678,33,21,45,76,89,09,3,3,23,Who would you describe this data?Saturday, 20 April 13
  8. 8. Descriptive statisticsDescriptive statistics are used to summarise,organise and describe data obtained from researchTest A -1,7,22,66,4,3,55,44,5,6,78,789,23,1,23,Test B -67,43,67,678,33,21,45,76,89,09,3,3,23,Who would you describe this data?Saturday, 20 April 13
  9. 9. Descriptive Statistics1) Percentages2) Measures of central tendency3) Spread of scores4) Measures of Variability5) Graphs and tables (Later in the AOS)Saturday, 20 April 13
  10. 10. Calculating thepercentageNumber of times score occurs DIVIDED BYTotal number of scores in data setMULTIPLIED BY 100E.G. The percentage of rolling a 6 would be:13/80 = 0.1625 x 100 = 16.25%Saturday, 20 April 13
  11. 11. Tells us how the data are clustered near the centralpoint of the dataset.There are three measures of central tendency1) Mean - average of all the scores (calculated byadding up all the scores and dividing that total by thenumber of scores)2) Median - the score that occurs exactly halfwaybetween the lowest and the highest score.3) Mode - the most commonly occurring score in thedataset.2) Measures of Central Tendency(Measures in the Bell Curve)Saturday, 20 April 13
  12. 12. Saturday, 20 April 13
  13. 13. 3) Spread of scoresAnother way of describing data is by looking athow the scores are spread. This is known asvariability. This can be done byRange - The range of data can be calculated bysubtracting the lowest score from the highestscoreStandard deviation - How far is each individualpiece of data from the mean. A low standarddeviation indicates the scores cluster around themeanSaturday, 20 April 13
  14. 14. Complete Check your understanding questions onpage 23 (RM book) - 10 minSaturday, 20 April 13
  15. 15. Inferential StatisticsInferential Statistics are used once the descriptivestatistics have identified there is a difference(variation) from the mean. (Read page 30 of RM book)What next is to determine if this difference orvariance is significant, or is it just due to chance.Inferential tests give a probability that the differenceis caused by chance.This is expressed as a p value.Generally the lower the p value the better, howeverp<0.05 (that is 5 times in 100 or 5% of the time it isdue to chance) is widely accepted.Saturday, 20 April 13
  16. 16. p = 0.03 means there are 3 chances in 100 (3%)that this difference would be achieved by chancealone.If the level of significance is p<0.05 then theseresults can be said to be statistically significant as itis less then (<) 0.05If the p value = 0.3 then the results are notsignificant as 0.3 is greater then 0.05.Saturday, 20 April 13
  17. 17. Complete questions on page 31 (RM book) 10 minSaturday, 20 April 13

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