Which of the following statements about research on management by objectives $($MBO$)$ is correct?

Question $2$ options:

$1)$

There have been few studies on the results of MBO.

$2)$

Research results have revealed mixed effects on productivity, with almost as many negative results as positive results.

$3)$

Improvement in productivity following an MBO program is strongly related to the level of commitment by top management.

$4)$

Research has shown strong effects of MBO on employee job satisfaction.