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Using SPSS for Chi Square

Using SPSS for Chi Square. UDP 520 Lab 5 Lin Lin November 8 th , 2007. Outline . Dataset Review t-test Chi-square Exercise . BMI. Body mass index (BMI) is a measure of body fat based on height and weight that applies to both adult men and women. Under & normal weight: BMI <25

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Using SPSS for Chi Square

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  1. Using SPSS for Chi Square UDP 520 Lab 5 Lin Lin November 8th, 2007

  2. Outline • Dataset • Review t-test • Chi-square • Exercise

  3. BMI • Body mass index (BMI) is a measure of body fat based on height and weight that applies to both adult men and women. • Under & normal weight: BMI <25 • Overweight & obesity: BMI ≥ 25

  4. Dataset – WLTP • 1000 adults aged 18+ (males and females) were recruited to study the effectiveness of Weight Loss Training Program (WLTP) • Variables • Sex (female=1) • BMI_1(before WLTP) • BMI_2(after WLTP) • Urban or suburban (urban=1) • Overweight_1 (overweight before WLTP) (overweight=1) • Overweight_2 (overweight after WLTP) (overweight=1) http://courses.washington.edu/urbdp520/UDP520/WLTP.sav

  5. Question 1 • Is BMI significantly different between people who live in an urban area and those who live in a suburb area before WLTP? Independent samples t-test

  6. Question 1 – Step by Step • Step 1: Making assumptions and meeting test requirements • Sampling is random • Level of measurement is interval-ratio • Sampling distribution is normal • Step 2: Stating the null hypothesis • Step 3: Selecting the sampling distribution and establishing the critical region • Sampling distribution = Z distribution • Alpha = 0.05, two-tailed • Z(critical) = ±1.96

  7. Question 1 (cont.)Step 4: Computing the test statisticin SPSS

  8. Question 1 (cont.) • Step 5: Making a decision and interpreting the results of the test Indicate whether result is significant or not (based on your predetermined alpha) Result (Z obtained)

  9. Question 2 • Is there any relationship between living in a suburban area and being overweight before WLTP? • Under & normal weight: BMI <25 • Overweight & obese: BMI ≥ 25 Chi Square test

  10. Question 2 – Step by Step • Step 1: Making assumptions and meeting test requirements • Random sampling • Level of measurement is nominal • Step 2: Stating the null hypothesis • H0: Living in an urban area and being overweight are independent • Ha: Living in an urban area and being overweight are dependent • Step 3: Selecting the sampling distribution and establishing the critical region • Sampling distribution = χ2 distribution • Alpha = 0.05 • Df = (r-1)(c-1) = 1 (a 2-by-2 table) • χ2 (critical) = 3.481

  11. Question 2 (cont.)Step 4: computing the test statistic in SPSS

  12. Question 2 (cont.) • Step 5: making a decision and interpreting the results of the test Result (χ2 obtained)

  13. Question 2 (cont.) The nominal symmetric measures indicate both the strength and significance of the relationship between the row and column variables of a crosstabulation.

  14. Exercise • Does a significant relationship exist between living in a suburban area and being overweight after WLTP? • Does a significant relationship exist between being a male and overweight before WLTP? • Does a significant relationship exist between being a male and overweight after WLTP?

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