Demographic and Health Survey 1990 - Nigeria

Abstract
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The 1990 Nigeria Demographic and Health Survey (NDHS) is a nationally representative survey conducted by the Federal Office of Statistics with the aim of gathering reliable information on fertility, family planning, infant and child mortality, maternal care, vaccination status, breastfeeding, and nutrition. Data collection took place two years after implementation of the National Policy on Population and addresses issues raised by that policy.

Fieldwork for the NDHS was conducted in two phases: from April to July 1990 in the southern states and from July to October 1990 in the northern states. Interviewers collected information on the reproductive histories of 8,781 women age 15-49 years and on the health of their 8,113 children under the age of five years.

OBJECTIVES

The Nigeria Demographic and Health Survey (NDHS) is a national sample survey of women of reproductive age designed to collect data on socioeconomic characteristics, marriage patterns, history of child bearing, breastfeeding, use of contraception, immunisation of children, accessibility to health and family planning services, treatment of children during episodes of illness, and the nutritional status of children.

The primary objectives of the NDHS are:

(i) To collect data for the evaluation of family planning and health programmes;
(ii) To assess the demographic situation in Nigeria; and
(iii) To support dissemination and utilisation of the results in planning and managing family planning and health programmes.

MAIN RESULTS

According to the NDHS, fertility remains high in Nigeria; at current fertility levels, Nigerian women will have an average of 6 children by the end of their reproductive years. The total fertility rate may actually be higher than 6.0, due to underestimation of births. In a 1981/82 survey, the total fertility rate was estimated to be 5.9 children per woman.

One reason for the high level of fertility is that use of contraception is limited. Only 6 percent of married women currently use a contraceptive method (3.5 percent use a modem method, and 2.5 percent use a traditional method). These levels, while low, reflect an increase over the past decade: ten years ago just 1 percent of Nigerian women were using a modem family planning method. Periodic abstinence (rhythm method), the pill, IUD, and injection are the most popular methods among married couples: each is used by about 1 percent of currently married women. Knowledge of contraception remains low, with less than half of all women age 15-49 knowing of any method.

Certain groups of women are far more likely to use contraception than others. For example, urban women are four times more likely to be using a contraceptive method (15 percent) than rural women (4 percent). Women in the Southwest, those with more education, and those with five or more children are also more likely to be using contraception.

Levels of fertility and contraceptive use are not likely to change until there is a drop in desired family size and until the idea of reproductive choice is more widely accepted. At present, the average ideal family size is essentially the same as the total fertility rate: six children per woman. Thus, the vast majority of births are wanted. The desire for childbearing is strong: half of women with five children say that they want to have another child.

Another factor leading to high fertility is the early age at marriage and childbearing in Nigeria. Half of all women are married by age 17 and half have become mothers by age 20. More than a quarter of teenagers (women age 15-19 years) either are pregnant or already have children.

National statistics mask dramatic variations in fertility and family planning between urban and rural areas, among different regions of the country, and by women's educational attainment. Women who are from urban areas or live in the South and those who are better educated want and have fewer children than other women and are more likely to know of and use modem contraception. For example, women in the South are likely to marry and begin childbearing several years later than women in the North. In the North, women continue to follow the traditional pattern and marry early, at a median age of 15, while in the South, women are marrying at a median age of 19 or 20. Teenagers in the North have births at twice the rate of those in the South: 20 births per 1130 women age 15-19 in the North compared to 10 birdas per 100 women in the South. Nearly half of teens in the North have already begun childbearing, versus 14 percent in South. This results in substantially lower total fertility rates in the South: women in the South have, on average, one child less than women in the North (5.5 versus 6.6).

The survey also provides information related to maternal and child health. The data indicate that nearly 1 in 5 children dies before their fifth birthday. Of every 1,000 babies born, 87 die during their first year of life (infant mortality rate). There has been little improvement in infant and child mortality during the past 15 years. Mortality is higher in rural than urban areas and higher in the North than in the South. Undemutrition may be a factor contributing to childhood mortality levels: NDHS data show that 43 percent of the children under five are chronically undemourished. These problems are more severe in rural areas and in the North.

Preventive and curative health services have yet to reach many women and children. Mothers receive no antenatal care for one-third of births and over 60 percent of all babies arc born at home. Only one-third of births are assisted by doctors, trained nurses or midwives. A third of the infants are never vaccinated, and only 30 percent are fully immunised against childhood diseases. When they are ill, most young children go untreated. For example, only about one-third of children with diarrhoea were given oral rehydration therapy.

Women and children living in rural areas and in the North are much less likely than others to benefit from health services. Almost four times as many births in the North are unassisted as in the South, and only one-third as many children complete their polio and DPT vaccinations. Programmes to educate women about the need for antenatal care, immunisation, and proper treatment for sick children should perhaps be aimed at mothers in these areas,

Mothers everywhere need to learn about the proper time to introduce various supplementary foods to breastfeeding babies. Nearly all babies are breastfed, however, almost all breastfeeding infants are given water, formula, or other supplements within the first two months of life, which both jeopardises their nutritional status and increases the risk of infection.

Geographic coverage
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The 1990 Nigeria Demographic and Health Survey (NDHS) is a nationally representative survey. The sample was constructed so as to provide national estimates as well as estimates for the four Ministry of Health regions.

Analysis unit
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- Household
- Women age 15-49
- Children under five years

Universe
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The population covered by the 1990 DHS is defined as the universe of all women age 15­-49 in Nigeria.

Kind of data
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Sample survey data

Sampling procedure
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The NDHS Sample was drawn from the National Master Sample for the 1987/1992 National Integrated Survey of Households (NISH) programme being implemented by the Federal Office of Statistics (FOS). NISH, as part of the United Nations National Household Survey Capability Programme, is a multi- subject household-based survey system.

The NISH master sample was created in 1986 on the basis of the 1973 census enumeration areas (EA). Within each state, EAs were stratified into three sectors (urban, semiurban, and rural), from which an initial selection of approximately 8C0 EAs was made from each state. EAs were selected at this stage with equal probability within sectors. A quick count of households was conducted in each of the selected EAs, and a final selection of over 4,000 EAs was made over the entire country, with probability proportional to size. This constitutes the NISH master sample from which the NDHS EAs were subsampled.

Prior to the NDHS selection of EAs, the urban and semiurban sectors of NISH were combined into one category, while the rural retained the NISH classification. A sample of about 10,000 households in 299 EAs was designed with twofold oversampling of the urban stratum, yielding 132 urban EAs and 167 rural EAs. The sample was constructed so as to provide national estimates as well as estimates for the four Ministry of Health regions.

The NDHS conducted its own EA identification and listing operation; a new listing of housing units and households was compiled in each of the selected 299 EAs. For each EA, a list of the names of the head of households was constructed, from which a systematic sample of 34 households was selected to be interviewed. A fixed number of 34 households per EA was taken in order to have better control of the sample size (given the variability in EA size of the NISH sample). Thus, the NDHS sample is a weighted sample, maintaining the twofold over sampling of the urban sector.

Mode of data collection
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Face-to-face

Research instrument
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Three questionnaires were used in the main fieldwork for the NDHS: a) the household questionnaire, b) the individual questionnaire, and c) the service availability questionnaire. The first two questionnaires were adapted from the DHS model B questionnaire, which was designed for use in countries with low contraceptive prevalence. The questionnaires were developed in English, and then translated into six of the major Nigerian languages: Efik, Hausa, Igbo, Kanuri, Tiv, and Yoruba.

a) All usual members and visitors in the selected households were listed on the household questionnaire. For each person listed, information was collected on age, sex, education, and relationship to the head of household. The household questionnaire was used to identify women eligible for the individual questionnaire.

b) The individual questionnaire was administered to women age 15-49 who spent the night preceding the household interview in the selected household. Information in the following areas was obtained during the individual interview:
1. Background characteristics of the respondent
2. Reproductive behaviour and intentions
3. Knowledge and use of contraception
4. Breastfeeding, health, and vaccination status of children
5. Marriage
6. Fertility preferences
7. Husband's background and woman's work
8. Height and weight of children under five.

c) The service availability questionnaire was implemented in the service availability survey (SAS), a separate activity from the main fieldwork. The SAS was designed to assess the availability (or supply) of health and family planning services. Thus, while the individual questionnaire collected information from female respondents pertaining to the demand for health and family planning services, the service availability (SA) questionnaire collected information pertaining to the supply of these services by canvassing health and family planning facilities. The SA questionnaire was administered at the community level (enumeration area), and information was gathered from two sources: groups of four or five knowledgeable informants in the selected community (assembled by the interviewer), and informants interviewed at facilities visited by the interviewer.

Cleaning operations
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Data processing staff for the NDHS consisted of four data entry clerks and one supervisor;, all were FOS staff. They were given periodic assistance by the DHS staff. Four IBM microcomputers were installed in the project office, FOS, Federal Secretariat and were used to process the data. All data entry occurred in the project office in Lagos.

Before questionnaires were passed for data entry, office editing was conducted. This entailed checking for internal consistency of responses recorded in the questionnaire, that skip instructions were properly followed, that there were no omissions, and that all entries were legible. This hastened the work of data entry staff.

Data entry started in April and was completed in October 1990. Once all the data had been entered, a final edit was conducted by running a computer programme to check for inconsistencies, and corrections were made (when possible) by referencing the original questionnaire. This final edit was completed in December 1990. The preliminary report was published in March 1991

Response rate
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A total of 9,998 households were selected; of these, 8,999 were successfully interviewed. The shortfall is largely due to households being absent; for which a predominant cause seemed to be for purposes of planting crops. In the interviewed households 9,200 eligible women were identified and 8,781 were successfully interviewed.

Sampling error estimates
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Sampling errors, on the other hand, can be evaluated statistically. The sample of women selected in the NDHS is only one of many samples that could have been selected from the same population, using the same design and expected size. Each of these samples would yield results that differ somewhat from the results of the actual sample selected. The sampling error is a measure of the variability between all possible samples. Although the degree of variability is not known exactly, it can be estimated from the survey results.

Sampling error is usually measured in terms of the standard error for a particular statistic (mean, percentage, etc.), which is the square root of the variance. The standard error can be used to calculate confidence intervals within which the true value for the population can reasonably be assumed to fall. For example, for any given statistic calculated from a sample survey, the value of that statistic will fall within a range of plus or minus two times the standard error of that statistic in 95 percent of all possible samples of identical size and design.

If the sample of women had been selected as a simple random sample, it would have been possible to use straightforward formulas for calculating sampling errors. However, the NDHS sample is the result of a two-stage stratified design, and, consequently, it was necessary to use more complex formulas. The computer package CLUSTERS, developed by the International Statistical Institute for the World Fertility Survey, was used to compute the sampling errors with the proper statistical methodology.

In addition to the standard errors, CLUSTERS computes the design effect (DEFT) for each estimate, which is defined as the ratio between the standard error using the given sample design and the standard error that would result if a simple random sample had been used. A DEFT value of 1.0 indicates that the sample design is as efficient as a simple random sample, while a value greater than 1.0 indicates the increase in the sampling error due to the use of a more complex and less statistically efficient design. CLUSTERS also computes the relative error and confidence limits for the estimates.

Sampling errors for the NDHS are calculated for selected variables considered to be of primary interest. The results are presented in an appendix to the Final Report for the country as a whole, for urban and rural areas, and for the four health zones: Northeast, Northwest, Southeast, and Southwest. For each variable, the type of statistic (mean or proportion) and the base population are given in Table B. 1 of the Final Report. Tables B.2 to B.8 present the value of the statistic (R), its standard error (SE), the number of unweighted (N) and weighted (WN) cases, the design effect (DEFT), the relative standard error (SE/R), and the 95 percent confidence limits (R~SE), for each variable.

In general, the relative standard errors of most estimates for the country as a whole are small, except for estimates of very small proportions. There are some differentials in the relative standard error for the estimates of sub-populations such as geographical areas. For example, for the variable EVBORN (children ever born to women aged 15-49), the relative standard error as a percent of the estimated mean for the whole country, for urban areas and for the Southeast zone is 1.5 percent, 2.3 percent, and 2.7 percent, respectively.

The confidence interval (e.g., as calculated for EVBORN) can be interpreted as follows: the overall average from the national sample is 3.311 and its standard error is .051. Therefore, to obtain the 95 percent confidence limits, one adds and subtracts twice the standard error to the sample estimate, i.e., 3.311+.102. There is a high probability (95 percent) that the true average number of children ever born to all women aged 15 to 49 is between 3.209 and 3.413.

Data appraisal
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Nonsampling error is the result of mistakes made in implementing data collection and data processing, such as failure to locate and interview the correct household, misunderstanding of the questions on the part of either the interviewer or the respondent, or data entry errors. Although numerous efforts were made during the implementation of the NDHS to minimize this type of error, nonsampling errors are impossible to avoid and difficult to evaluate statistically.

摘要
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1990年尼日利亚人口与卫生调查（NDHS）是由联邦统计局实施的一项全国性代表性调查，旨在收集关于生育、计划生育、婴儿和儿童死亡率、孕产妇保健、疫苗接种状况、母乳喂养和营养等方面的可靠信息。数据收集在实施国家人口政策两年后进行，旨在回应该政策提出的问题。

实地调查分为两个阶段：1990年4月至7月在南部各州进行，7月至10月在北部各州进行。调查员收集了8,781名15-49岁女性的生育史信息以及8,113名5岁以下儿童的卫生健康信息。

目标

尼日利亚人口与卫生调查（NDHS）是一项针对育龄女性的全国性抽样调查，旨在收集有关社会经济特征、婚姻模式、生育史、母乳喂养、避孕药具使用、儿童疫苗接种、获得卫生和计划生育服务、疾病期间儿童的诊疗以及儿童营养状况的数据。

NDHS的主要目标如下：

(i) 收集数据以评估计划生育和卫生项目；
(ii) 评估尼日利亚的 demographic状况；
(iii) 支持在计划和管理计划生育和卫生项目时传播和利用调查结果。

主要结果

根据NDHS的调查结果，尼日利亚的生育率仍然很高；在当前的生育率水平下，尼日利亚女性在其生育年龄结束时平均将拥有6个孩子。由于出生的低估，总生育率实际上可能高于6.0。在1981/82年的调查中，总生育率估计为每名女性5.9个孩子。

生育率水平较高的一个原因是避孕药具的使用有限。目前只有6%的已婚女性使用避孕方法（其中3.5%使用现代方法，2.5%使用传统方法）。尽管这些比例相对较低，但与过去十年相比有所上升：十年前只有1%的尼日利亚女性使用现代计划生育方法。在已婚夫妇中，周期性禁欲（节律法）、避孕药丸、宫内节育器和注射剂是最受欢迎的方法，每种方法都由大约1%的已婚女性使用。避孕知识的普及率仍然很低，不到所有15-49岁女性中有一半的人知道任何避孕方法。

某些女性群体比其他群体更有可能使用避孕药具。例如，城市女性使用避孕方法的可能性（15%）是农村女性的四倍（4%）。西南部、受教育程度较高的女性以及有五个或更多孩子的女性也更可能使用避孕药具。

生育率和避孕药具的使用水平不太可能改变，直到理想家庭规模下降，直到生殖选择观念得到更广泛的接受。目前，平均理想家庭规模基本上与总生育率相同：每名女性六个孩子。因此，绝大多数的出生都是预期的。生育的愿望很强烈：一半有五个孩子的女性表示她们还想再要一个孩子。

导致生育率高的另一个因素是尼日利亚婚姻和生育的年龄过早。所有女性中有一半在17岁之前结婚，一半在20岁之前成为母亲。超过四分之一的青少年（15-19岁的女性）要么怀孕，要么已经育有子女。

全国统计数据掩盖了城市和农村地区、国家不同地区以及女性教育水平之间的生育率和计划生育方面的巨大差异。来自城市地区或居住在南部以及受教育程度较高的女性，她们想要的和拥有的孩子比其他女性少，并且更有可能了解并使用现代避孕药具。例如，南部女性的结婚和生育年龄通常比北部女性晚几年。在北部，女性继续遵循传统模式，在平均年龄15岁时结婚，而在南部，女性的结婚年龄平均为19或20岁。北部青少年的生育率是南部青少年的两倍：北部15-19岁的女性中每1130人就有20个出生，而南部每100人就有10个出生。北部近一半的青少年已经开始了生育，而南部只有14%。这导致南部的总生育率显著低于北部：南部女性的平均生育率比北部女性低一个孩子（5.5比6.6）。

调查还提供了有关孕产妇和儿童健康的信息。数据显示，几乎五分之一的儿童在五岁之前死亡。每出生1000个婴儿中，有87个在出生后的第一年内死亡（婴儿死亡率）。在过去15年中，婴儿和儿童的死亡率几乎没有改善。死亡率在农村地区高于城市地区，在北部高于南部。营养不良可能是导致儿童死亡率水平的一个因素：NDHS数据显示，五岁以下儿童中43%患有慢性营养不良。这些问题在农村地区和北部地区更为严重。

预防和治疗性卫生服务尚未惠及许多妇女和儿童。三分之一的女性的分娩没有接受产前护理，超过60%的所有婴儿在家中出生。只有三分之一的分娩由医生、受过培训的护士或助产士协助。三分之一的婴儿从未接种疫苗，只有30%的儿童完全接种了儿童疾病疫苗。当儿童生病时，大多数年轻儿童得不到治疗。例如，只有大约三分之一的腹泻儿童接受了口服补液疗法。

居住在农村地区和北部的妇女和儿童比其他人更不可能从卫生服务中受益。北部地区的出生中，有四分之一是没有得到协助的，而南部地区只有六分之一。只有三分之一的儿童完成了脊灰和百白破疫苗接种。也许应该针对这些地区的母亲开展关于需要产前护理、免疫接种和患病儿童正确治疗的宣传教育项目。

所有地方的妇女都需要了解在母乳喂养婴儿时引入各种补充食品的正确时间。尽管几乎所有婴儿都是母乳喂养的，但几乎所有在出生后的前两个月内接受母乳喂养的婴儿都被给予了水、配方奶粉或其他补充品，这不仅危害了他们的营养状况，还增加了感染的风险。

地理覆盖范围
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1990年尼日利亚人口与卫生调查（NDHS）是一项全国性代表性调查。样本的设计是为了提供全国估计以及四个卫生部门地区的估计。

分析单元
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- 家庭
- 15-49岁的女性
- 5岁以下的儿童

总体
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1990年DHS所涵盖的人口被定义为所有15-49岁尼日利亚女性的总体。

数据类型
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样本调查数据

抽样程序
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NDHS样本是从1987/1992年全国综合家庭调查（NISH）项目的国家主样本中抽取的，该项目由联邦统计局（FOS）实施。NISH作为联合国国家家庭调查能力项目的一部分，是一个多主题基于家庭的调查系统。

NISH主样本是在1986年基于1973年人口普查区（EA）创建的。在每个州内，EA被分为三个部门（城市、半城市和农村），从中从每个州中选择约800个EA。在这一阶段，在各部门内以等概率选择EA。在每个选定的EA中进行了快速的家庭计数，并在整个国家范围内选择了超过4000个EA，其选择概率与规模成比例。这构成了NISH主样本，从中抽取了NDHS EA样本。

在NDHS EA选择之前，NISH的城市和半城市部门被合并为一个大类，而农村则保留了NISH的分类。在299个EA中设计了大约10,000个家庭的样本，城市层级的抽样增加了两倍，产生了132个城市EA和167个农村EA。样本的设计是为了提供全国估计以及四个卫生部门地区的估计。

NDHS进行了自己的EA识别和列表操作；在每个选定的299个EA中编制了新的住房单位和家庭列表。对于每个EA，建立了一个家庭户主名单，从中选择了34个家庭进行访谈。每个EA中选择34个家庭是为了更好地控制样本量（考虑到NISH样本EA大小的可变性）。因此，NDHS样本是一个加权样本，保持了城市部门的两倍抽样。

数据收集方式
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面对面

研究工具
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NDHS主要实地调查中使用了三个问卷：a）家庭问卷，b）个人问卷和c）服务可用性问卷。前两个问卷是从用于低避孕率国家的DHS模型B问卷中改编的。问卷是用英语开发的，然后翻译成了尼日利亚六大主要语言：伊基、豪萨、伊博、卡努里、蒂夫和约鲁巴。

a）家庭问卷上列出了选定家庭的所有通常成员和访客。对于列出的每个人，收集了年龄、性别、教育和与家庭户主的关系等信息。家庭问卷用于确定适合个人问卷的合格女性。

b）个人问卷是对在家庭访谈前一个晚上在选定家庭过夜的15-49岁女性进行的。在个人访谈中获得了以下领域的信息：
1. 响应者的背景特征
2. 生殖行为和意图
3. 避孕知识的掌握和使用
4. 儿童的母乳喂养、健康和疫苗接种状况
5. 婚姻
6. 生育偏好
7. 丈夫的背景和女性的工作
8. 5岁以下儿童的身高和体重。

c）服务可用性问卷是在服务可用性调查（SAS）中实施的，这是一项与主要实地调查分开的活动。SAS旨在评估卫生和计划生育服务的可用性（或供应）。因此，尽管个人问卷收集了与卫生和计划生育服务需求相关的女性受访者的信息，但服务可用性（SA）问卷通过调查卫生和计划生育设施收集了有关这些服务供应的信息。SA问卷在社区层面（人口普查区）进行，信息来自两个来源：在选定的社区中由调查员组织的四或五名知识渊博的知情者（组）以及调查员访问的设施中接受访谈的知情者。

数据清理操作
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NDHS的数据处理人员由四名数据录入员和一名主管组成；他们都是FOS的员工。他们得到了DHS员工的定期协助。在项目办公室、FOS、联邦秘书处安装了四台IBM微型计算机，用于处理数据。所有数据录入都在拉各斯的项目办公室进行。

在问卷传递给数据录入员之前，进行了办公室编辑。这包括检查问卷中记录的响应的内部一致性、跳过指令是否得到适当遵循、是否存在遗漏以及所有条目是否可读。这加快了数据录入人员的工作。

数据录入始于4月，并于1990年10月完成。一旦所有数据都已录入，就通过运行计算机程序来检查不一致性，并尽可能通过参考原始问卷进行纠正。这项最终编辑于1990年12月完成。初步报告于1991年3月发布。

响应率
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共选择了9,998个家庭；其中，8,999个家庭成功接受了访谈。缺额主要归因于家庭缺席；主要原因似乎是种植作物的需要。在访谈的家庭中，确定了9,200名合格女性，其中8,781人成功接受了访谈。

抽样误差估计
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另一方面，抽样误差可以从统计上进行评估。NDHS中选定的女性样本只是从同一总体中可以选出的许多样本之一，使用相同的设计和预期规模。每个这样的样本都会产生与实际选定的样本结果略有不同的结果。抽样误差是衡量所有可能样本之间差异的指标。尽管变异程度无法确切知晓，但可以从调查结果中估计出来。

抽样误差通常用特定统计量（均值、百分比等）的标准误差来衡量，这是方差的平方根。标准误差可用于计算置信区间，其中可以合理地假设总体真实值落在该区间内。例如，对于从样本调查中计算的任何给定统计量，该统计量的值将在95%的所有可能样本（具有相同大小和设计）的标准误差的两倍范围内。

如果女性样本被选为简单随机样本，则可以使用简单的公式来计算抽样误差。但是，NDHS样本是两阶段分层设计的产物，因此有必要使用更复杂的公式。用于世界生育率调查的国际统计研究所开发的计算机程序CLUSTERS被用来使用正确的统计方法计算抽样误差。

除了标准误差外，CLUSTERS还为每个估计值计算了设计效应（DEFT），定义为使用给定样本设计时的标准误差与如果使用简单随机样本将产生的标准误差之间的比率。DEFT值为1.0表示样本设计与简单随机样本一样高效，而大于1.0的值表示由于使用更复杂且统计效率较低的样本设计而增加的抽样误差。CLUSTERS还计算估计值的相对误差和置信限。

NDHS的抽样误差是为考虑为主要感兴趣变量的选定变量计算的。结果在国家的最终报告中以附录的形式呈现，包括城市和农村地区以及东北、西北、东南和西南四个卫生区。对于每个变量，表B.1中的最终报告给出了统计量类型（均值或比例）和基数人口。

总的来说，大多数估计值的相对标准误差都很小，除了非常小的比例估计值。对于子群体（如地理区域）的估计值，相对标准误差存在一些差异。例如，对于变量EVBORN（15-49岁女性的生育子女总数）而言，相对于整个国家、城市地区和东南区的估计均值的相对标准误差分别为1.5%、2.3%和2.7%。

置信区间（例如，如EVBORN所计算的）可以这样解释：国家样本的平均值为3.311，其标准误差为.051。因此，为了获得95%的置信限，将两倍的标准误差加到或从样本估计值中减去，即3.311±.102。有很高的可能性（95%）认为，所有15至49岁女性生育的子女总数真实平均值在3.209和3.413之间。

数据评估
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非抽样误差是由于在实施数据收集和数据处理过程中出现的错误而产生的，例如未能找到和访谈正确的家庭、访谈员或受访者对问题的误解，或数据录入错误。尽管在实施NDHS过程中做出了许多努力来最大限度地减少此类错误，但非抽样误差是不可避免的，且难以进行统计评估。