Figure 1.
Green vegetation (left) absorbs visible light and reflects near-infrared light; Sparse vegetation (right) reflects more visible light and less near-infrared light.
The NDVI is the ratio of absorbed visible light and reflected near-infrared to the total amount of visible and near infrared radiation striking a surface.
Figure 2.
Massachusetts population distribution based on the 2010 U.S. Census.
Red to green indicate higher to lower populated areas.
Figure 3.
NDVI values for year 2012 (March 21) and location of schools included in this study.
Green to red represents the greenness level from high to low.
Table 1.
Population of the five major cities of Massachusetts in 2013.
Table 2.
Descriptive statistics of the 905 schools in Massachusetts during 2006 to 2012 (n = 6333).
Table 3.
Coefficients (estimates with 95% confidence interval) of NDVI of (A) March, (B) July, and (C) October in GLMMs.
Figure 4.
Stratified analysis for NDVI coefficients (estimates with 95% confidence interval) for (A) English and (B) Math models according to the median of percentage of low income of the study schools.
The categorized female variable is based on the median levels of low income percentage (above or below median). NDVI is highly significant in all of the models (p<0.01).
Figure 5.
Stratified analysis for NDVI coefficients (estimates with 95% confidence interval) for (A) English and (B) Math models according to the median of percentage of female of the study schools.
The categorized female variable is based on the median levels of female percentage (above or below median). NDVI is highly significant in all of the models (p<0.01) excepted for the estimate for poorer/math with 500 m buffer distance (p = 0.07).