Results
Part 3. Preliminary Results
Descriptive Statistics
Table 1 shows descriptive statistics for life expectancy at birth and the quantitative predictors. The total average life expectancy was:
2012: 70.2 years (sd= 8.5) with a minimum life expectancy at birth of 48.8 years and a maximum of 83.1 years.
2013: 70.5 years (sd= 8.3) with a minimum life expectancy at birth of 48.9 years and a maximum of 83.3 years.
Table 1. Descriptive Statistics for Data Analytic Variables, 2012-2013 (N=195)
Bivariate Analyses
Scatter plots for the association between the total life expectancy response variable and quantitative predictors (Figure 1, Figure 2) revealed that life expectancy was longer for the countries with larger GDP or adj. net income per capita. If we take a logarithm for the predictors, we get a more linear relationship with a larger value of the Pearson's correlation coefficient (see table 2).
Table 2. Pearson’s correlation coefficients
Total life expectancy and also the values of this index for men and women are shown in Figure 3 (data is presented for 2012-2013).
Figure 3. Total life expectancy
ANOVA results (see Figure 4) indicated that total life expectancy differ significantly as a function of GDP group (see Table 3).
Figure 4. ANOVA results
Table 3. ANOVA results
Regression Analysis
Fig. 5-6 show regression models constructed from the original features and their logarithms. The best quality is shown by models constructed on the basis of logarithmic features. The quality of models built on the basis of predictor 1 (GDP or log GDP per capita) and predictor 2 (adjusted net national income or log adjusted net national income per capita) is approximately the same.
Figure 5. Regression Analysis (data 2012)
Figure 6. Regression Analysis (data 2013)
Log adjusted net national income per capita was most strongly associated with total life expectancy at birth (Table 4-5).
Table 4. Variable names and regression coefficients:
Table 5. R-square from training and test data
Mean square error (MSE) for each fold is shown on Figure 7.
Figure 7. MSE
Total life expectancy at birth was shorter for the countries that had less values of GDP or adjusted net national income per capita. The higher values of these indicators correspond to a longer total life expectancy for the respective countries. These predictors accounted for 63% of the variance in total life expectancy.