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How to run ANOVA on SPSS

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How to run ANOVA on SPSS

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How to run ANOVA on SPSS

  1. 1. Running ANOVA on SPSS http://www.palmx.org/drtamil/spss/ sga-ttest-youtube.sav
  2. 2. ©drtamil@gmail.com 2016 Factors Affecting SGA SGA (Y/N) (Birth weight) Mother’s Nutrition (BMI/Obesity) •Weight •Height Smoking Hypertension
  3. 3. ©drtamil@gmail.com 2016 Dependent Outcome  Birth weight of the babies  Small for gestational age i.e. less than 2.7kg for term babies – Y/N By Yehudamalul - Own work, CC BY-SA 3.0,
  4. 4. ©drtamil@gmail.com 2016 What test to use?  Conduct the appropriate statistical test to test whether there is any association between Classification of Weight (OBESCLAS) and BIRTH WEIGHT (in kg).
  5. 5. ©drtamil@gmail.com 2016 Factors Affecting SGA Outcome (Birth weight in kg) Proxy for Mother’s Nutrition (OBESCLAS) - underweight - normal -overweight Smoking (Y/N) Hypertension (Y/N)
  6. 6. ©drtamil@gmail.com 2016 What test to use?  Birth weight – interval/continuous data.  Body Mass Index is classified into ◦ Underweight ◦ Normal weight ◦ Overweight Therefore it is categorical data.  Basically we are comparing the mean babies birth weight between underweight, normal and overweight mothers.  Assuming birth weight is normally distributed, most suitable test is ANOVA.
  7. 7. ©drtamil@gmail.com 2016 Comparing birth weight distribution
  8. 8. Running ANOVA on SPSS http://www.palmx.org/drtamil/spss/ sga-ttest-youtube.sav
  9. 9. ©drtamil@gmail.com 2016 Comparing mean birth weight Underweight 2.4 + 0.3 Normal 2.7 + 0.5 Overweight 3.1 + 0.6
  10. 10. ©drtamil@gmail.com 2016 Levene’s Test for Equality of Variances tests the condition that the variances of both samples are equal. If it is significant as above (p<0.05) then the variances are unequal. Therefore, for post-hoc, the Bonferroni procedure can’t be used, as it assumes equal variances. Since we have a large sample size, the Bonferroni test can be used if interpreted with care. Implication of Homogeneity test
  11. 11. ©drtamil@gmail.com 2016 Significant diff of means, p < 0.05
  12. 12. ©drtamil@gmail.com 2016 Sig. diff. of means, but between which and which group? Post-hoc!
  13. 13. ©drtamil@gmail.com 2016 Birth weight of babies born to Underweight mothers are significantly lower than babies born to Normal & Overweight mothers. Birth weight of babies born to Normal mothers are significantly lower than babies born to Overweight mothers. Implication of post-hoc test
  14. 14. ©drtamil@gmail.com 2016 Conclusion  Babies of Underweight mothers has significantly lower birth weight (2.4 + 0.3) compared to babies of Normal (2.7 + 0.5 )and Overweight mothers (3.1 + 0.6).  Babies of Normal mothers has significantly lower birth weight (2.7 + 0.5) compared to babies of Overweight mothers (3.1 + 0.6).  The difference is statistically significant since p value smaller than 0.05.  “Big Mothers Get Big Babies!”
  15. 15. ©drtamil@gmail.com 2016 Exercise  Repeat the same statistical test between; ◦ Type of Work and Birth Weight

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