Table 1.
Response rates for the greywater use survey
| Type of approach | Number of approaches | Number of responses | Crude response rate (%) | Adjusted number of approaches | Adjusted number of responses | Adjusted response rate (%) and (95% CI) |
|---|---|---|---|---|---|---|
| Postal survey personalised |
5,500 |
511 |
9.3 |
5,500 |
575* |
10.5 (9.7-11.3) |
| Postal survey generic |
4,000 |
266 |
6.7 |
4,000 |
299* |
7.5 (6.7-8.3) |
| Internet survey personalised |
10,000 |
289 |
2.9 |
6,210** |
289 |
4.7 (4.2-5.2) |
| Internet survey generic |
7,000 |
101 |
1.4 |
4,515*** |
101 |
2.2 (1.8-2.6) |
| Telephone survey personalised |
1,000 |
273 |
27.3 |
903**** |
273 |
30.2 (27.2-33.2) |
| Total | 34,500 | 1621 | 4.7 | 25,384 | 1,621 | 6.4 (6.1-6.7) |
* Adjusted by distribution of 97 postal surveys with unknown postcode to personalised (n = 64) or generic modes (n = 33) as per survey response rates for known postcodes.
** 62.1% of households in the personalised internet survey area had internet access.
*** 64.5% of households in the generic internet survey area had internet access.
**** Crude response rate calculated for 1,000 telephone numbers (minimum quantity for data file purchase), adjusted rate is for 903 telephone numbers with at least one contact attempt made. Of 866 households contacted, 352 refused, 148 were missed call backs, 93 had language difficulties. There were 37 numbers with technical difficulties.