Choosing the best statistical tests for your data and hypotheses. Dr. Christine Pereira Academic Skills Team (ASK)

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1 Choosing the best statistical tests for your data and hypotheses Dr. Christine Pereira Academic Skills Team (ASK)

2 Which test should I use? T-tests Correlations Regression Dr. Christine Pereira ASK Academic Skills ( ) 2

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8 Variables measured using WORDS or CATEGORIES Categorical Variables measured using NUMBERS Interval/Ratio Nominal (Unranked categories) Marital Status Political Party Eye Color Ordinal (Ranked categories) Satisfaction level Level of agreement Scale Height Weight Age No. of cars No. of students Dr. Christine Pereira ASK Academic Skills ( ) 8

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10 The tests should depend on Your hypotheses The level of measurement of the variables stated in your hypotheses Dr. Christine Pereira ASK Academic Skills ( ) 10

11 You will not be able to answer your main research question with one statistical test. Consumer experience of a brand impacts brand loyalty You should have several hypotheses to test. The results of these tests will answer your main research question. Brand Pleasure Purchase Intention Brand Dominance H 1 H 2 H 3 Brand Loyalty Dr. Christine Pereira ASK Academic Skills ( ) 11

12 For each hypothesis, identify the variables from your data that will be used. Note the level of measurement for each variable. Brand Pleasure H 1 Brand Loyalty Brand Pleasure positively impacts Brand Loyalty Scale Scale Dr. Christine Pereira ASK Academic Skills ( ) 12

13 Identify what each hypothesis is investigating: Comparing 2 or more groups? A relationship, association, impact or effect? A model for predicting an outcome? Correlation Brand Pleasure H 1 Brand Loyalty Brand Pleasure positively impacts Brand Loyalty Dr. Christine Pereira ASK Academic Skills ( ) 13

14 Brand Loyalty Survey.sav Dr. Christine Pereira ASK Academic Skills ( ) 14

15 Comparing 2 or more Groups Testing differences between means Dr. Christine Pereira ASK Academic Skills ( ) 15

16 Is there a significant difference in Brand Dominance between Age groups? Younger participants experience greater Brand Dominance than older participants Dr. Christine Pereira ASK Academic Skills ( ) 16

17 Is there a significant difference in Brand Dominance between Age groups? Dependent Variable Scale or Ordinal? Independent Variable 2 groups or 3+ groups? 2 groups 3+ groups Scale Independent t-test One-way ANOVA Ordinal Mann Whitney U Kruskal-Wallis Dr. Christine Pereira ASK Academic Skills ( ) 17

18 Is there a significant difference in Brand Loyalty between current iphone users compared to users of other brands? Consumers who currently use an iphone are more Brand Loyal than those who do not Dr. Christine Pereira ASK Academic Skills ( ) 18

19 Is there a significant difference in Brand Loyalty between current iphone users compared to users of other brands? Dependent Variable Scale or Ordinal? Independent Variable 2 groups or 3+ groups? 2 groups 3+ groups Scale Independent t-test One-way ANOVA Ordinal Mann Whitney U Kruskal-Wallis Dr. Christine Pereira ASK Academic Skills ( ) 19

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21 Dataset codes: 0 = Currently does not use iphone 1 = Current iphone user Dr. Christine Pereira ASK Academic Skills ( ) 21

22 The means are different BUT is the difference big enough to be statistically significant? 1 Levene s Test for Equality of Variances p > 0.05: Read t-test results from top row: Equal variances assumed p < 0.05: Read t-test results from bottom row: Equal variances not assumed Dr. Christine Pereira ASK Academic Skills ( ) 22

23 The means are different BUT is the difference big enough to be statistically significant? 2 p > 0.05: Brand Loyalty is NOT significantly different for iphone users compared to users of other brands. p < 0.05: Brand Loyalty IS significantly different for iphone users compared to users of other brands. Dr. Christine Pereira ASK Academic Skills ( ) 23

24 Is there a significant difference in Brand Loyalty between current iphone users compared to users of other brands? Conclusion: There is evidence to suggest that there is a significant difference in Brand Loyalty between iphone users and non-iphone users (p=.000). p < 0.05 Significant difference Dr. Christine Pereira ASK Academic Skills ( ) 24

25 Boxes are similar to the t-test See SPSS Survival Manual by Julie Pallant for how to run and interpret the output from this test Test variable Find this book in the library here: e-book OR Hard Copy Grouping variable Dr. Christine Pereira ASK Academic Skills ( ) 25

26 See SPSS Survival Manual by Julie Pallant for how to run and interpret the output from this test Boxes are the same as for a t-test Find this book in the library here: e-book OR Hard Copy Dr. Christine Pereira ASK Academic Skills ( ) 26

27 See SPSS Survival Manual by Julie Pallant for how to run and interpret the output from this test Boxes are the same as for a t-test Find this book in the library here: e-book OR Hard Copy Dr. Christine Pereira ASK Academic Skills ( ) 27

28 Significant Correlations A relationship, association, impact or effect Dr. Christine Pereira ASK Academic Skills ( ) 28

29 Measure the strength of a relationship They only measure association They do NOT imply causation!

30 There s a significant relationship between Brand Pleasure and Brand Loyalty Brand Pleasure positively impacts Brand Loyalty People who experience higher levels of Brand Pleasure are more Brand Loyal This is also an association question, even though it doesn t explicitly say so Dr. Christine Pereira ASK Academic Skills ( ) 31

31 There s a significant relationship between Brand Pleasure and Brand Loyalty Scale Ordinal Nominal Dichotomous (exactly 2 groups) Scale Ordinal Nominal Pearson s r Spearman s rho Compare groups Pearson s r Spearman s rho Spearman s rho Chi-square & Cramer s V Spearman s rho Compare groups Chi-square & Cramer s V Chi-square & Cramer s V Chi-square & Cramer s V Dichotomous (exactly 2 groups) Pearson s r Spearman s rho Chi-square & Cramer s V Chi-square test & Phi Dr. Christine Pereira ASK Academic Skills ( ) 32

32 There s a significant relationship between BP2 (Brand Pleasure Item 2) and PI3 (Purchase Intention Item 3) Variable name in SPSS Q5_BP2 Q6_PI3 Dr. Christine Pereira ASK Academic Skills ( ) 33

33 There s a significant relationship between BP2 (Brand Pleasure Item 2) and PI3 (Purchase Intention Item 3) BP2 positively impacts PI3 People who experience greater pleasure from a brand are more likely to consider it their first choice of smartphone Q5_BP2 Q6_PI3 Dr. Christine Pereira ASK Academic Skills ( ) 34

34 There s a significant relationship between BP2 (Brand Pleasure Item 2) and PI3 (Purchase Intention Item 3) BP2 positively impacts PI3 People who experience greater pleasure from a brand are more likely to consider it their first choice of smartphone This is also an association question, even though it doesn t explicitly say so Dr. Christine Pereira ASK Academic Skills ( ) 35

35 There s a significant relationship between BP2 (Brand Pleasure Item 2) and PI3 (Purchase Intention Item 3) Scale Ordinal Nominal Dichotomous (exactly 2 groups) Scale Ordinal Nominal Pearson s r Spearman s rho Compare groups Pearson s r Spearman s rho Spearman s rho Chi-square & Cramer s V Spearman s rho Compare groups Chi-square & Cramer s V Chi-square & Cramer s V Chi-square & Cramer s V Dichotomous (exactly 2 groups) Pearson s r Spearman s rho Chi-square & Cramer s V Chi-square test & Phi Dr. Christine Pereira ASK Academic Skills ( ) 36

36 There s a significant relationship between current brand of smartphone and Brand Dominance The brand of smartphone currently used impacts how dominate that brand is in a person s everyday life People who currently use iphones experience greater Brand Dominance than people using other brands. This could be an association question or a comparing groups question, depending on the level of measurement of variables Dr. Christine Pereira ASK Academic Skills ( ) 37

37 There s a significant relationship between current brand of smartphone and Brand Dominance Scale Ordinal Nominal Dichotomous (exactly 2 groups) Scale Ordinal Nominal Pearson s r Spearman s rho Compare groups Pearson s r Spearman s rho Spearman s rho Chi-square & Cramer s V Spearman s rho Compare groups Chi-square & Cramer s V Chi-square & Cramer s V Chi-square & Cramer s V Dichotomous (exactly 2 groups) Pearson s r Spearman s rho Chi-square & Cramer s V Chi-square test & Phi Dr. Christine Pereira ASK Academic Skills ( ) 38

38 There s a significant relationship between current brand of smartphone and Brand Dominance There is a significant difference in Brand Dominance based on the brand of smartphone one currently uses Scale Ordinal Nominal Dichotomous (exactly 2 groups) Scale Ordinal Nominal Pearson s r Spearman s rho Compare groups Pearson s r Spearman s rho Spearman s rho Chi-square & Cramer s V Spearman s rho Compare groups Chi-square & Cramer s V Chi-square & Cramer s V Chi-square & Cramer s V Dichotomous (exactly 2 groups) Pearson s r Spearman s rho Chi-square & Cramer s V Chi-square test & Phi Dr. Christine Pereira ASK Academic Skills ( ) 39

39 Brand Loyalty Survey There s a significant relationship between Brand Pleasure and Brand Loyalty Pearson s r Dr. Christine Pereira ASK Academic Skills ( ) 40

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41 These are the 2 variables we want to correlate Brand Loyalty Survey Dr. Christine Pereira ASK Academic Skills ( ) 42

42 Brand Loyalty Survey These will always be 1. Never report these values. Dr. Christine Pereira ASK Academic Skills ( ) 43

43 Brand Loyalty Survey These will always be the same. Just report one of these. Dr. Christine Pereira ASK Academic Skills ( ) 44

44 Strength Between -1 to +1 Brand Loyalty Survey Significance (p-value) Dr. Christine Pereira ASK Academic Skills ( ) 45

45 Strong relationships Moderate/weak relationships Y Y.5 to 1 X.3 to.49 X Y Y -.3 to to -1 X X Dr. Christine Pereira ASK Academic Skills ( ) 46

46 Sign of correlation Strong Moderate Weak Very weak or None + values 0.5 to to to to values -1.0 to to to to 0 Strong & Positive Dr. Christine Pereira ASK Academic Skills ( ) 47

47 Strong & Positive Brand Loyalty Survey p < 0.05 Significant p < 0.05: There IS a significant relationship between the 2 variables p > 0.05: There is NOT a significant relationship between the 2 variables Dr. Christine Pereira ASK Academic Skills ( ) 48

48 Conclusion: There is evidence to suggest a significant strong positive relationship between BP and BL. There s a significant relationship between Brand Pleasure and Brand Loyalty Brand Loyalty Survey Strong & Positive p < 0.05 Significant Dr. Christine Pereira ASK Academic Skills ( ) 49

49 Conclusion: There is evidence to suggest a significant strong positive relationship between BP and BL. People who experience more BP tend to be more BL People who experience less BP tend to be less BL Dr. Christine Pereira ASK Academic Skills ( ) 50

50 Brand Loyalty Survey There s a significant relationship between BP2 (Brand Pleasure Item 2) & PI3 (Purchase Intention Item 3) Spearman s rho Dr. Christine Pereira ASK Academic Skills ( ) 51

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52 These are the 2 variables we want to correlate Brand Loyalty Survey Dr. Christine Pereira ASK Academic Skills ( ) 53

53 Brand Loyalty Survey These will always be 1. Never report these values. Dr. Christine Pereira ASK Academic Skills ( ) 54

54 Brand Loyalty Survey These will always be the same. Just report one of these. Dr. Christine Pereira ASK Academic Skills ( ) 55

55 Brand Loyalty Survey Strength Between -1 to +1 Significance (p-value) p < 0.05: There IS a significant relationship between the 2 variables p > 0.05: There is NOT a significant relationship between the 2 variables Dr. Christine Pereira ASK Academic Skills ( ) 56

56 Sign of correlation Strong Moderate Weak Very weak or None + values 0.5 to to to to values -1.0 to to to to 0 Strong & Positive Dr. Christine Pereira ASK Academic Skills ( ) 57

57 Brand Loyalty Survey Strong & Positive p < 0.05 Significant p < 0.05: There IS a significant relationship between the 2 variables p > 0.05: There is NOT a significant relationship between the 2 variables Dr. Christine Pereira ASK Academic Skills ( ) 58

58 Conclusion: There is evidence to suggest a significant strong positive relationship between BP2 and PI3. There s a significant relationship between BP2 (Brand Pleasure Item 2) & PI3 (Purchase Intention Item 3) Brand Loyalty Survey Strong & Positive p < 0.05 Significant Dr. Christine Pereira ASK Academic Skills ( ) 59

59 Conclusion: There is evidence to suggest a significant strong positive relationship between BP and BL. People who experience more brand pleasure tend to consider the brand their 1 st choice People who experience less brand pleasure tend not to consider the brand their 1 st choice Dr. Christine Pereira ASK Academic Skills ( ) 60

60 How to compute Pearson s r How to interpret the output Dr. Christine Pereira ASK Academic Skills ( ) 61

61 How to compute Spearman s How to interpret the output Dr. Christine Pereira ASK Academic Skills ( ) 62

62 Chi-square + interpretation Chi-square + interpretation (assumptions violated) Dr. Christine Pereira ASK Academic Skills ( ) 63

63 Making Predictions Dr. Christine Pereira ASK Academic Skills ( ) 64

64 Use regression when You want to test a relationship btwn 3+ variables You want to use one or more IVs to predict an outcome (DV) You have a model that looks something like this: Construct 1 Construct 2 Outcome Construct 3 Dr. Christine Pereira ASK Academic Skills ( ) 65

65 Brand Pleasure, Purchase Intention and Brand Dominance impact Brand Loyalty Does Brand Pleasure, Purchase Intention or Brand Dominance have the greatest impact on Brand Loyalty? Brand Pleasure, Purchase Intention and Brand Dominance are significant predictors of Brand Loyalty Dr. Christine Pereira ASK Academic Skills ( ) 66

66 Brand Pleasure, Purchase Intention and Brand Dominance impact Brand Loyalty Independent variables MUST be scale or dichotomous The dependent variable MUST be scale Dr. Christine Pereira ASK Academic Skills ( ) 67

67 What if the dependent variable isn t scale? Is it dichotomous (categorical with 2 groups)? Use logistic regression Is it ordinal? Use ordinal regression This may help: Is it nominal with 3 or more groups? Use multinomial regression **Check out IBM SPSS for Intermediate Statistics from the library for all of these methods Dr. Christine Pereira ASK Academic Skills ( ) 68

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69 Brand Loyalty Survey Dr. Christine Pereira ASK Academic Skills ( ) 70

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73 Brand Pleasure, Purchase Intention and Brand Dominance impact Brand Loyalty Brand Loyalty Survey Dr. Christine Pereira ASK Academic Skills ( ) 74

74 The residuals should be approximately normally distributed. If not, the model is not reliable This is close enough so we can use the results of the regression Residual = Error Predicted Actual for each observation Dr. Christine Pereira ASK Academic Skills ( ) 75

75 The IVs can t be strongly correlated with each other This is a strong correlation so we can t use Brand Pleasure and Purchase Intention as IVs together Dr. Christine Pereira ASK Academic Skills ( ) 76

76 The IVs can t be highly correlated with each other If two IVs have a correlation stronger than.7 or -.7 then you can t use both as IVs at the same time you ll need to choose one. Check which IV is having the greatest impact on the DV Usually, one of the IVs will be significant and the other won t be significant Dr. Christine Pereira ASK Academic Skills ( ) 77

77 Is the model any good at predicting the DV? Brand Loyalty Survey p > 0.05, model IS NOT significant it IS NOT good at predicting your DV p < 0.05, model IS significant it IS good at predicting your DV Dr. Christine Pereira ASK Academic Skills ( ) 78

78 If the model is significant (p < 0.05), then report R and Adj R^2 Brand Loyalty Survey Dr. Christine Pereira ASK Academic Skills ( ) 79

79 If the model is significant (p < 0.05), then report R and Adj R^2 Brand Loyalty Survey R= Correlation between your predicted DV values and the actual DV values in the data set Dr. Christine Pereira ASK Academic Skills ( ) 80

80 Brand Loyalty Survey Actual DV Predicted DV R= Correlation between your predicted DV values and the actual DV values in the data set Dr. Christine Pereira ASK Academic Skills ( ) 81

81 If the model is significant (p < 0.05), then report R and Adj R^2 Brand Loyalty Survey Example:.921 suggests there is a very strong relationship between the predicted and actual DVs (i.e. our model is very good). Dr. Christine Pereira ASK Academic Skills ( ) 82

82 If the model is significant (p < 0.05), then report R and Adj R^2 Brand Loyalty Survey Adj R2 x 100% = Percentage of variation in the DV that can be explained by the model Dr. Christine Pereira ASK Academic Skills ( ) 83

83 If the model is significant (p < 0.05), then report R and Adj R^2 Brand Loyalty Survey Example:.826 x 100% = 82.6% of the variation in Brand Loyalty can be explained by Brand Pleasure, Purchase Intention, and Brand Dominance. Dr. Christine Pereira ASK Academic Skills ( ) 84

84 If the model is significant (p < 0.05), check if each IV is significant Brand Loyalty Survey p > 0.05, IV is NOT significant it is NOT a good predictor of the DV p < 0.05, IV IS significant it IS a good predictor of the DV Dr. Christine Pereira ASK Academic Skills ( ) 85

85 If the model is significant (p < 0.05), check if each IV is significant Brand Loyalty Survey Purchase Intention is the ONLY good predictor p > 0.05, IV is NOT significant it is NOT a good predictor of the DV p < 0.05, IV IS significant it IS a good predictor of the DV Dr. Christine Pereira ASK Academic Skills ( ) 86

86 Brand Loyalty Survey Run regression again WITH only Purchase Intention Dr. Christine Pereira ASK Academic Skills ( ) 87

87 If the model is significant (p < 0.05), check if each IV is significant Brand Loyalty Survey Purchase Intention is significant It is a good predictor of Brand Loyalty Dr. Christine Pereira ASK Academic Skills ( ) 88

88 If the model is significant (p < 0.05), check if each IV is significant Brand Loyalty Survey Use B values to write your prediction equation DV (Brand Loyalty) = *PurchaseIntention Dr. Christine Pereira ASK Academic Skills ( ) 89

89 This model didn t work now what? Maybe it s not the right model try this instead Brand Pleasure Brand Dominance Brand Pleasure Purchase Intention Brand Dominance Run another regression: DV: Purchase Intention Purchase Intention Brand Loyalty IVs: Brand Pleasure and Brand Dominance Brand Loyalty Dr. Christine Pereira ASK Academic Skills ( ) 90

90 Tick same options as before Dr. Christine Pereira ASK Academic Skills ( ) 91

91 Examine output in the same way as before Let s examine the Coefficients table: Brand Pleasure is significant It is a good predictor of Purchase Intention Dr. Christine Pereira ASK Academic Skills ( ) 92

92 Examine output in the same way as before Let s examine the Coefficients table: Brand Dominance is NOT significant It is a NOT good predictor of Purchase Intention Dr. Christine Pereira ASK Academic Skills ( ) 93

93 The final model: Brand Pleasure Excluded constructs: Brand Dominance Don t Panic!! Purchase Intention Brand Loyalty An insignificant result (p>0.05) does not mean our work is rubbish. It just means it s not what we thought it would be. All research is interesting, even if it s not what we expect. Smartphone brands would be interested to know that BP influences PI and PI influences BL! Dr. Christine Pereira ASK Academic Skills ( ) 94

94 Survey Data Choosing a test.pdf Dr. Christine Pereira ASK Academic Skills ( ) 95

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96 SPSS Survival Manual, 4 th Edition (2010) by Julie Pallant. E-book: Library shelf location: HA32.P SPSS Survival Manual, 5 th Edition (2013) by Julie Pallant. Library shelf location: HA32.P SPSS Survival Manual, 6 th Edition (2016) by Julie Pallant. Library shelf location: HA32.P Dr. Christine Pereira ASK Academic Skills ( ) 97

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