Probability and Significance Unit 4 Research Methods Learning

Probability and Significance Unit 4 – Research Methods

Learning Objectives Use knowledge from previous lessons to answer past exam questions on hypotheses Explain why psychologists use inferential statistics Define what is meant by probability & identify different levels of probability (e. g. p=0. 05) Outline which level of probability and significance psychologists use AND why Outline what is meant by type 1 and type 2 errors Identify and justify the use of FOUR inferential statistics used in Psychology

Starter – Past exam questions Answer the exam questions based on yesterday’s lesson on hypotheses Swap your answers Peer mark using mark scheme Any targets?

Probability and Significance Lets imagine we notice that history students are more sociable than psychology students Write a suitable hypothesis and remember to operationalise…

Probability and Significance Go through the worksheet completing the tasks

Type 1 error A type 1 error refers to a situation in which we assume that our findings show something when they don’t! = rejecting a null hypothesis that is true = wrongly accepting the alternative hypothesis =assuming the results were due to the IV when they were in fact due to chance Therefore we should have kept the null hypothesis rather than rejecting it! K. Christopher, La Retraite School

Type 2 error A type 2 error refers to a situation in which we may miss something that is actually happening! = accepting a null hypothesis that is false = wrongly rejecting the alternative hypothesis =assuming the results were due to chance when they were in fact due to the IV Therefore we should have rejected the null hypothesis rather than accepting it! K. Christopher La Retraite School

Test your knowledge If we reject the null hypothesis when it is actually true, we are making a… The significance level normally set in psychology is… For a result to be significant, the test statistic must be equal to or ______ than the critical value How do we define probability? If we accept the alternate hypothesis when it is actually false, we are making a…

Inferential Statistics To decide on the statistical test, we first need to think about the type of data we have…. Is it: Nominal Ordinal Interval/ratio Each of you has a particular data type – describe this type and use an example

Nominal data

Ordinal data

Interval/ratio data

Which Test? Using your booklet and textbook, create a poster/information sheet to help researchers know which test to use This should include - The four tests - Which data type they use – with a brief description of the data - Which experimental design is used – with a brief definition of each design

1. Which test would you use? Participant number New Mathematics Help Scheme Participant number No Scheme implemented 1 11 11 14 2 12 12 13 3 9 13 12 4 8 14 16 5 11 15 14 6 14 16 15 7 10 17 19 8 7 18 20 9 15 19 16 10 9 IV = Whether or not given Maths help Scheme DV = Maths test score

2. Which test would you use? Participant Study time (mins) Test score (%) 1 100 60 2 25 47 3 95 70 4 60 53 5 10 41 6 75 51 7 80 61 8 45 44 9 55 45 10 85 61

3. Which test would you use? Participant number Neutral Words Emotionally threatening words 1 14 15 2 18 16 3 19 19 4 20 14 5 16 19 6 15 10 7 20 16 8 18 15 9 19 18 10 20 18 IV = Whether word presented is neutral or emotionally threatening DV = Recall of words

4. Which test would you use? Art Students Science Students Row Total Extroverted 19 10 29 Introverted 11 15 26 Column Total 30 25 Total: 55 IV = Whether Art Students or Science Students (Natural Experiment) DV = Extroversion. Introversion score

Answers 1. Mann Whitney 2. Spearman’s rho 3. Wilcoxon 4. Chi square

Your Task Complete the past exam questions on inferential statistics

Learning Objectives Use knowledge from previous lessons to answer past exam questions on hypotheses Explain why psychologists use inferential statistics Define what is meant by probability & identify different levels of probability (e. g. p=0. 05) Outline which level of probability and significance psychologists use AND why Outline what is meant by type 1 and type 2 errors Identify and justify the use of FOUR inferential statistics used in Psychology