Suppose I have the list with elements (either 1 or 4 as the last digit) as follows:

data=
{{42, 49.11, 1}, {41, 49.32, 4}, {41, 48.21, 4}, {41, 53.08, 1}, {39, 
  46.22, 1}, {39, 47.06, 1}, {47, 48.87, 4}, {41, 49.64, 1}, {41, 
  48.44, 1}, {42, 49.98, 4}, {39, 49.04, 1}, {46, 48.73, 1}, {49, 
  48.33, 4}, {39, 50.95, 1}, {42, 46.05, 4}, {49, 52.52, 1}, {49, 
  48.81, 1}, {49, 50.75, 4}, {47, 52.39, 1}, {41, 52.56, 1}, {40, 
  56.01, 4}, {46, 52.77, 4}, {43, 52.81, 1}, {39, 50.37, 1}, {40, 
  52.38, 1}, {49, 51.31, 4}, {48, 54.26, 4}, {40, 53.3, 4}, {42, 
  50.62, 4}, {48, 49.66, 4}, {43, 51.39, 4}, {41, 59.23, 4}, {41, 
  49.07, 4}, {40, 51.43, 4}, {39, 54.47, 4}, {49, 50.4, 4}, {48, 
  51.04, 1}, {46, 47.95, 1}, {45, 50.52, 4}, {44, 53.18, 1}}

How do I break it into two sets with the same last digit, such that

data1={{42, 49.11, 1},  {41, 53.08, 1}, {39, 
  46.22, 1}, {39, 47.06, 1}, {41, 49.64, 1}, {41, 
  48.44, 1}, {39, 49.04, 1}, {46, 48.73, 1}, {39, 50.95, 1}, 
 {49, 52.52, 1}, {49, 48.81, 1}...}

and

data2={{41, 49.32, 4}, {41, 48.21, 4}, {47, 48.87, 4},{42, 49.98, 4}, {49, 
  48.33, 4},  {42, 46.05, 4}, {49, 50.75, 4},  {40,   56.01, 4}, {46, 52.77, 4}..}

How do I test whether these two data sets are linearly independent?