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  1. 1. 2(ii) Spearman’s RHO A-Level Psychology, Research Methods: “How to do the statistical tests” Spearman’s Rank Order Correlation Coefficient What is it and when is it used? Spearman’s Rho is used when we are trying to find a ____________________ between two ____ _____________________. The two sets of data have to be _______________. The level of measurement also has to produce ______________data. Examples Is there a relationship between the cost of chocolate and the taste? Hypotehsise! Experimental: ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ Null: ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ Probability level I am willing to accept is_____ Table to show___________________________ Graph to show______________________________________ __________________________________________ ___________________________________________________ (Complete with scores) What do your descriptive results tell you? ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ (If we didn’t have a correlation, let’s pretend we did for the purposes of the next bit!) Now for the inferential stats!
  2. 2. Complete all activities up to and including the NULL HYPOTHESIS on your worksheet. Correlation Variable Positive Correlation Negative Correlation Zero Correlatio n An analysis of the strength of a relationship between two variables When there is no relationship between the variables A factor of thing that can change-it varies. March 8, 2019 Title: Research Methods: Correlations AND hypotheses As one variable increases or decreases, the other does the same Spearman’s Rank Order Correlation Coefficient What is it and when is it used? Spearman’s Rho is used when we are trying to find a ____________________ between two ____ _____________________. The two sets of data have to be _______________. The level of measurement also has to produce ______________data. Examples Is there a relationship between the cost of chocolate and the taste? Hypotehsise! Experimental: ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ Null: ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ Probability level I am willing to accept is_____ Table to show___________________________ Graph to show______________________________________ __________________________________________ ___________________________________________________ (Complete with scores) What do your descriptive results tell you? ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ (If we didn’t have a correlation, let’s pretend we did for the purposes of the next bit!) Now for the inferential stats!
  3. 3. Answers Correlation Variable Positive Correlation Zero Correlatio n An analysis of the strength of a relationship between two variables When there is no relationship between the variables A factor of thing that can change- it varies. . March 8, 2019 As one variable increases or decreases, the other does the same
  4. 4. Apply it! March 8, 2019
  5. 5. Some basic information:  A statistical test performed to see if the calculated correlation coefficient (rs figure) is significant  The coefficient is calculated from related data (usually two measures about the same person) and can be on a scale from +1 through to -1.  Where +1 is a perfect positive correlation and -1 is a perfect negative correlation.
  6. 6. Spearman’s RHO Conditions for use:  When co-variables are collected for a correlation study  When scale data has been converted into ordinal data (ranked)  Not suitable to use with ‘tied ranks’  Correlations are always related, pairs of data
  7. 7. Remember-for correlations we do not have IV and DV Co-variables What are the 2 co-variables for this study; Researchers wanted to investigate how the frequency of illness affected an employees professional development in the workplace. Co-variable 1: illness (absenteeism) Co-Variable 2: professional development (salary increases, promotions, appraisals)March 8, 2019
  8. 8. chocolate!chocolate! Is there a correlation between theIs there a correlation between the price of chocolate and how tastyprice of chocolate and how tasty it is?it is? What could weWhat could we predictpredict about theabout the relationship between the cost ofrelationship between the cost of chocolate and it’s taste?chocolate and it’s taste? March 8, 2019 There’s only one way to find out!!!!!
  9. 9. What would you need to control? Blind test, type of chocolate, amount eaten How/what would you operationalise the co-variables? Taste (sweetness? Texture?)score /5 and weight Ethical Considerations? Allergies, freedom to withdraw
  10. 10. Name: Taste score out of 5 (1 not tasty- 5 delicious) choc1 choc 2 choc 3 choc 4 choc 5 March 8, 2019 Name: Taste score out of 5 (1 not tasty- 5 delicious) choc 1 choc 2 choc 3 choc 4 choc 5 Name: Taste score out of 5 (1 not tasty- 5 delicious) choc 1 choc 2 choc 3 choc 4 choc 5 Name: Taste score out of 5 (1 not tasty- 5 delicious) choc 1 choc 2 choc 3 choc 4 choc 5
  11. 11. Collate the class scores... Calculate MEAN taste scores for each choc! March 8, 2019
  12. 12. March 8, 2019 The actual order of price (PER 100g) choc 1 choc 2 choc 3 choc 4 choc 5 5 1 4 3 2 Order of eating! #chocolate#chocolate Price in bhtPrice in bht per 100gper 100g Mean tasteMean taste scorescore 11 40 2.4 22 70 2 33 89 3.4 44 110 3.8 55 139 3.5
  13. 13. Some data collected in a correlation study Hypothesis (simplified): Negative correlation between happiness and time spent on internet socializing #chocolate#chocolate Price in bhtPrice in bht per 100gper 100g Mean tasteMean taste scorescore 11 40 2.4 22 70 2 33 89 3.4 44 110 3.8 55 139 3.5
  14. 14. March 8, 2019 Chocolate Taste score 1 2.4 Correlation Coefficient = 0.815139 2 2 3 3.4 4 3.8 5 3.5 0 0.5 1 1.5 2 2.5 3 3.5 4 0 1 2 3 4 5 6 TasteScore/5 Biscuit value A scattergraph to illustrate the relationship between chocolate price (per gram) and taste score out of 5 #chocolate#chocolate Price perPrice per 100g100g Mean tasteMean taste scorescore 11 40bht 2.4 22 70bht 2 33 89 3.4 44 110 3.8 55 139 3.5
  15. 15. Use half of your sheet to plot a scatterUse half of your sheet to plot a scatter graph to show the results.....graph to show the results..... Include....Include.... • A titleA title • Labels for the axesLabels for the axes • A written paragraph explainingA written paragraph explaining your results. So far, haveyour results. So far, have you met your hypothesis?you met your hypothesis? March 8, 2019
  16. 16. Here comes the science bit….
  17. 17. First calculate the sum of differences squared (⅀d²) ## a) Pricea) Price per 100gper 100g b) Mean Tasteb) Mean Taste scorescore c) Rank forc) Rank for column (a)column (a) d) Rank ford) Rank for column (b)column (b) Diff = dDiff = d (ra-rb)(ra-rb) d²d² 1 40 2.4 2 70 2 3 89 3.4 4 110 3.8 5 139 3.5 ⅀⅀ d²d²
  18. 18. Now complete the formula Where n = 6 and ⅀d² = 68 So r₂ = 1- (6 x 68) = 1-1.94 = -0.943 6(36-1) r₂ = -0.943 Coeficcient = 0.8151
  19. 19. Critical Value Table The calculated r : ________ is than₂ ______ so we can _______ the null and _________ our directional hypothesis at 5% (0.05) One tailed 0.05 0.025 n 0.10 0.05 0.02 5 0.900 1.000 1.000 Two tailed r₂ must be equal to or greater than the critical value
  20. 20. Now over to you

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