Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-0.11915 -0.04856 -0.02940  0.03882  0.23724 

Coefficients:
                     Estimate Std. Error t value    Pr(>|t|)    
(Intercept)           0.02942    0.01054   2.790    0.005980 ** 
xLow income           0.06731    0.01891   3.559    0.000504 ***
xLower middle income  0.08974    0.01639   5.475 0.000000189 ***
xNA                  -0.02940    0.07602  -0.387    0.699530    
xUpper middle income  0.05131    0.01613   3.180    0.001801 ** 
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.07529 on 144 degrees of freedom
Multiple R-squared:  0.1919,	Adjusted R-squared:  0.1694 
F-statistic: 8.548 on 4 and 144 DF,  p-value: 0.000003227