General household survey - Statistics South Africa

Statistics South Africa 50
P0318
• If the filter question had a missing value, the filter is allocated the value that corresponds with the
subsequent question which had a valid value.
• If the values of the filter question and subsequent question are inconsistent, the filter question’s
value is set to missing and imputed using either the hot-deck or nearest neighbour imputation
techniques. The imputed value is then once again tested against the skip rule. If the skip rule
remains violated the question subsequent to the filter question is dealt with by either setting it to
missing and imputing or if that fails printing a message of edit failure for further investigation,
decision-making and manual editing.
In cases where skip violations take place for questions where multiple questions follow the filter question,
the rules used are as follows:
• If the filter question has a missing value, the filter is allocated the value that corresponds with the
value expected given the completion of the remainder of the question set.
• If the filter question and the values of subsequent questions values were inconsistent, a counter is
set to see what proportion of the subsequent questions have been completed. If more than 50% of
the subsequent questions have been completed the filter question’s value is modified to
correspond with the fact that the rest of the questions in the set were completed. If less than 50%
of the subsequent questions in the set were completed, the value of the filter question is set to
missing and imputed using either the hot-deck or nearest neighbour imputation techniques. The
imputed value is then once again tested against the skip rule. If the skip rule remains violated the
questions in the set that follows the filter question are set to missing.
When dealing with internal inconsistencies as much as possible was done using logical imputation, i.e.
information from other questions is compared with the inconsistent information. If other evidence is found to
back up either of the two inconsistent viewpoints, the inconsistency is resolved accordingly. If the internal
consistency remains, the question subsequent to the filter question is dealt with by either setting it to
missing and imputing its value or printing a message of edit failure for further investigation, decisionmaking
and manual editing.
Two imputation techniques were used for imputing missing values: hot deck and nearest neighbour. In both
cases already published code was used for imputation. The variable composition of hot decks is based on
a combination of the variables used for the Census (where appropriate), an analysis of odds ratios and
logistic regression models. Generally, as in the QLFS system, the GHS adds geographic variables such as
province, geography type, metro/non-metro, population group, etc. to further refine the decks. This was not
done for Census 2001 and it is assumed that the reason for this is the differences in deck size and position
for sample surveys as opposed to a multi-million record database.
The ‘No’ imputations assume that if the ‘Yes’/’No’ question had to be completed and there is a missing
value next to any of the options the response should have been ‘No’. Missing values are therefore
converted to the code for ‘No’, namely ‘2’. This is only done if there is some evidence that the questions
have been completed. Otherwise all remain missing. For questions for which each option represents a
question, no ‘No’ imputations were made.
18.12 Definitions of terms
A household is a group of persons who live together and provide themselves jointly with food and/or other
essentials for living, or a single person who lives alone.
Note: The persons basically occupy a common dwelling unit (or part of it) for at least four nights in a week
on average during the past four weeks prior to the survey interview, sharing resources as a unit. Other
explanatory phrases can be 'eating from the same pot' and 'cook and eat together'.
Persons who occupy the same dwelling unit but do not share food or other essentials, are regarded as
separate households. For example, people who share a dwelling unit, but buy food separately, and
generally provide for themselves separately, are regarded as separate households within the same
dwelling unit.
Conversely, a household may occupy more than one structure. If persons on a plot, stand or yard eat
together, but sleep in separate structures (e.g. a room at the back of the house for single young male
members of a family), all these persons should be regarded as one household.
Multiple households occur when two or more households live in the same dwelling unit.
General Household Survey, July 2011