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Lab 1 Instruction

Lab 1 Instruction. Data Transformation, T-Tools and Alternatives. Topics. 1. Describing and Displaying Data 2. Data Transformations 3. Tests for Differences between Two Independent Samples / Two Paired Samples. 1.Displaying and Describing Data.

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Lab 1 Instruction

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  1. Lab 1 Instruction Data Transformation, T-Tools and Alternatives

  2. Topics • 1. Describing and Displaying Data • 2. Data Transformations • 3. Tests for Differences between Two Independent Samples / Two Paired Samples

  3. 1.Displaying and Describing Data • 3 principal procedures for describing and exploring continuous data: AnalyzeDescriptive statistics  Frequencies Descriptives Explore

  4. Frequencies procedure

  5. Descriptives procedure

  6. Explore Procedure • The Explore procedure in SPSS allows you to obtain descriptive statistics for your data, identify extreme observations, calculate the percentiles of the distribution, and display the data with a variety of plots.

  7. Explore Procedure

  8. Explore Procedure

  9. Explore Procedure

  10. Boxplots Single group

  11. Boxplot More than one groups (use labels)

  12. Boxplot

  13. Normality Plots – Q-Q Plots

  14. Describe the data • Center: mean; median • Spread: s.d.; IQR=Q3-Q1 • Shape: symmetric VS skewed (left/right) • Outliers: <Q1-1.5*IQR or >Q3+1.5*IQR • Normality according to boxplot/QQ plot/Kolmogorov-Smirnov test

  15. 2. Data Transformations Compute Variables e.g. Natural Logarithm Transform

  16. Natural Logarithm Transformation

  17. Other Useful Data Transformations • The type depends on the form of the distribution of the variable on the original scale. Some recommended data transformations :

  18. 3.Tests for Differences between Two Paired Samples used for paired (matched) data Paired-Samples T Test

  19. Read output

  20. 4. Tests for Differences between Two Independent Samples Independent-Samples T-Test

  21. Assume Equal variances or not?! ---- refer to Levene’s test result

  22. Tips for the assignment Generally~ Read the question carefully. Follow the marking schema

  23. Q4 & Q8 b Null hypothesis, Alternative hypothesis; value of the Test statistic; p-value; Conclusion; (maybe) Confidence interval. • Q8 a&c “the differences in LLSIR on the log scale between normal and hypoplastic lungs” VS “the ratio of mean LLSIR of normal lungs to that of hypoplastic lungs” use antilogrithm, see Page 16 in the instruction

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