The correct answer is: (i) and (iii)
Group bonus schemes are useful to reward performance when production is integrated so that all members of the group must work harder to increase output, for example in production line manufacture. Statement (i) is therefore true.
Group bonus schemes are not effective in linking the reward to a particular individual's performance. Even if one individual makes a supreme effort, this can be negated by poor performance from other members of the group. Therefore statement (ii) is not true.
Non-production employees can be included in a group incentive scheme, for example when all employees in a management accounting department must work harder to produce prompt budgetary control reports. Statement (iii) is therefore true.
