At Wave 4, this experiment tested different ways of getting respondents to register on the Understanding Society web-site using the delivery of the between wave mailing as a vehicle for achieving this via either e-mail for those who have given us an e-mail address or by traditional postal mailing. It also tested whether the use of incentives helps in this process; half of respondents were incentivized with a choice of incentive including a traditional high street voucher or vouchers for Amazon or iTunes, or a donation to one of three charities including Help for Heroes, Oxfam, or the NSPCC. Respondents without e-mail were re-allocated to the equivalent non-email treatment: “ff_alliwmw4” contains the experimental allocation whilst “ff_actiwmw4” contains the actual allocation given these rules. The IP4 refreshment sample was excluded from this experiment and has a blank value for both variables. The table below provided the control variables used in the experiment.
Table: Controlling variable for registration experiment
| ff_actiwmw4 | ||
|---|---|---|
| ff_alliwmw4 | ||
| Has E-mail? | No E-mail? | |
| No-incentive, paper | ff_actiwmw4 = 1 | ff_actiwmw4 = 1 |
| No-incentive, e-mail | ff_actiwmw4 = 2 | ff_actiwmw4 = 1 |
| Incentive, paper | ff_actiwmw4 = 3 | ff_actiwmw4 = 3 |
| Incentive, e-mail | ff_actiwmw4 = 4 | ff_actiwmw4 = 3 |
| ff_actiwmw4 = 5 (Already registered online) | ||
