SQL reduce execution time

The below SQL taking 3.5 to 4 Minutes. how I can reduce execution time..

SQL> set autotrace traceonly explain

SQL> select tp.test_instance_id,

  2         tp.param_group_id,

  3         tpg.parent_param_group_id,

  4      MAX(decode(tp.param_name, 'splitterRatio', tp.param_value)) splitterRatio,

  5      MAX(decode(tp.param_name, 'maxSplitterLoss', tp.param_value)) maxSplitterLoss,

  6      MAX(decode(tp.param_name, 'used', tp.param_value)) used

  7  from

  8      test_instance ti,

  9      test_parameter tp,

10      test_parameter_group tpg

11  where

12      ti.test_instance_id      = tp.test_instance_id

13      and ti.test_instance_id  = tpg.test_instance_id

14      and tpg.param_group_id   = tp.param_group_id