Call:
lm(formula = y ~ x)

Residuals:
      Min        1Q    Median        3Q       Max 
-0.032323 -0.019208 -0.008301  0.004012  0.241215 

Coefficients:
                      Estimate Std. Error t value Pr(>|t|)   
(Intercept)           0.008317   0.004793   1.735  0.08486 . 
xLow income           0.010918   0.008598   1.270  0.20619   
xLower middle income  0.024010   0.007452   3.222  0.00157 **
xNA                  -0.008301   0.034566  -0.240  0.81057   
xUpper middle income  0.019008   0.007336   2.591  0.01055 * 
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.03423 on 144 degrees of freedom
Multiple R-squared:  0.08079,	Adjusted R-squared:  0.05525 
F-statistic: 3.164 on 4 and 144 DF,  p-value: 0.01583