Data processing error
In November 2023, an error was identified on the 2021/22 New Zealand Health Survey (NZHS) dataset. The error meant that about 20% of households were assigned the wrong New Zealand Index of Deprivation (NZDep) decile. NZDep is used in the calculation of the survey weights, which are used in all analyses, so the error impacts all survey statistics.
How we corrected the error
The error was corrected by assigning the correct NZDep decile to the 2021/22 New Zealand Health Survey dataset, recalculating the survey weights, and recalculating the survey statistics.
Affected release
The error affected one release – the 2021/22 New Zealand Health Survey results published in November 2022. The corrected data is now available at:
- Annual Update of Key Results 2021/22: New Zealand Health Survey
- Annual Data Explorer. This online tool includes the published 2022/23 statistics, as well as the corrected 2021/22 statistics.
Updated versions of the 2021/22 confidentialised unit record file (CURF) will be provided to Stats NZ in 2024.
Impact of the error on statistics
The error affected nearly all survey statistics for 2021/22. However, the impact was relatively small in most cases and the corrected statistics were nearly all within the margin of error of the previously published statistics.
At a total population level, the corrected statistics were within 0.5 percentage point of the previously published statistics for 76% of indicators. Nearly all (92%) corrected statistics were within 1 percentage point of the previously published statistics. For a very small number of indicators (1%), differences were around 2 percentage points for a small number of indicators (1%). For example, among households with children the percentage who reported that food runs out sometimes or often changed from 12.5% to 14.4%. However, the revised statistic was within the margin of error for the previously published statistic (10.5–14.7%).
Differences between the previously published and corrected statistics were sometimes larger for population subgroups. However, the corrected statistics were nearly all within the margin of error for the previously published statistics. There were a few exceptions (11 out of about 10,000 combinations) and all of these were breakdowns by NZDep.
Larger differences by NZDep were expected because the error impacts the statistics in two ways. Firstly, it impacts via the survey weights. Secondly, it impacts because a slightly different group of respondents contribute to each NZDep quintile.
The following table shows the impact of the error on a selection of indicators from the 2021/22 New Zealand Health Survey.
| Indicator | Population group | Previously published | Corrected | Change | ||
|---|---|---|---|---|---|---|
| Percent | 95% CI | Percent | 95% CI | Percentage points | ||
| Self-rated health – good, very good, or excellent | Adults | 88.4 | 86.9–89.8 | 88.0 | 86.5–89.3 | -0.4 |
| Māori | 81.3 | 76.8–85.2 | 80.5 | 76.2–84.4 | -0.8 | |
| Pacific | 83.4 | 75.5–89.6 | 84.0 | 76.9–89.7 | 0.6 | |
| Psychological distress – high or very high | Adults | 11.2 | 9.9–12.6 | 11.6 | 10.3–13.0 | 0.4 |
| Māori | 17.8 | 14.4–21.7 | 18.5 | 14.9–22.5 | 0.7 | |
| Pacific | 14.4 | 9.0–21.4 | 14.8 | 9.3–22.0 | 0.4 | |
| Daily smoking | Adults | 8.0 | 7.0–9.0 | 8.6 | 7.7–9.7 | 0.6 |
| Māori | 19.9 | 16.5–23.7 | 21.3 | 17.7–25.3 | 1.4 | |
| Pacific | 18.2 | 11.8–26.1 | 18.1 | 12.1–25.4 | -0.1 | |
| Hazardous drinking | Adults | 18.8 | 17.3–20.3 | 18.7 | 17.3–20.2 | -0.1 |
| Māori | 33.2 | 28.6–38.1 | 33.4 | 28.8–38.3 | 0.2 | |
| Pacific | 21.7 | 15.7–28.9 | 21.5 | 15.3–28.7 | -0.2 | |
| Meets sleep duration recommendation | Adults | 68.9 | 67.0–70.7 | 68.3 | 66.6–70.1 | -0.6 |
| Māori | 59.7 | 54.7–64.6 | 59.1 | 54.1–63.9 | -0.6 | |
| Pacific | 62.3 | 53.2–70.8 | 61.0 | 51.9–69.5 | -1.3 | |
| Unmet need for GP due to cost | Adults | 10.7 | 9.7–11.8 | 11.1 | 10.2–12.1 | 0.4 |
| Māori | 14.5 | 11.6–17.8 | 14.9 | 11.9–18.2 | 0.4 | |
| Pacific | 11.4 | 6.4–18.4 | 11.0 | 6.3–17.5 | -0.4 | |
| Parent rated health – good, very good, or excellent | Children | 98.0 | 96.9–98.8 | 97.8 | 96.7–98.6 | -0.2 |
| Māori | 94.7 | 91.2–97.1 | 94.4 | 90.7–96.9 | -0.3 | |
| Pacific | 97.9 | 92.8–99.7 | 97.5 | 91.3–99.7 | -0.4 | |
| Meets sleep duration recommendation | Children | 77.4 | 74.1–80.4 | 76.2 | 72.8–79.4 | -1.2 |
| Māori | 72.9 | 66.6–78.7 | 72.4 | 66.2–78.0 | -0.5 | |
| Pacific | 66.4 | 54.6–76.8 | 64.2 | 51.6–75.5 | -2.2 | |
| Food runs out – often or sometimes | Children | 12.5 | 10.5–14.7 | 14.4 | 12.1–16.9 | 1.9 |
| Māori | 22.4 | 17.6–27.9 | 24.1 | 19.0–29.8 | 1.7 | |
| Pacific | 38.2 | 28.6–48.6 | 41.6 | 31.6–52.1 | 3.4 | |
Enquiries
For further information please contact: [email protected]
