Measurement error is the difference between the target population's characteristics and the measurement of these characteristics in a survey. There are two types of measurement error: systematic error and random error.
Systematic error is more serious than random error. Occurs when the survey responses are systematically different from the target population responses. For example, if a researcher only surveyed individuals who answered their phone between 9 and 5, Monday through Friday, the survey results would be biased toward individuals who are unemployed.
Sources of bias include
Nonobservational error -- Individuals in the target population are systematically excluded from the sample, such as in the example above.
Observational error -- When respondents systematically answer surveys question incorrectly. For example, surveys that ask respondents how much they weigh will probably underestimate the population's weight because respondents are likely to underreport their weight.
Random error is an expected part of survey research, and statistical techniques are designed to account for this sort of measurement error. Occurs because of natural and uncontrollable variations in the survey process, i.e., the mood of the respondent. For example, a researcher may administer a survey about marital happiness. However, some respondents may have had a fight with their spouse the evening prior to the survey, while other respondents' spouses may have cooked the respondent's favorite meal. The survey responses will be affected by the random day on which the respondents were chosen to participate in the study. With random error, the positive and negative influences on the survey measure balance out.
Ethics of Survey Research
Respondents should give informed consent before participating in a survey. In order for respondents to give informed consent, the researcher must inform the respondents of the study's purpose, content, duration, and potential risks and benefits. The researcher must inform the respondents that they do not have to answer all the survey questions. The researcher must inform the respondents that they can stop participating in the study at any point
Confidentiality and Anonymity
It is absolutely imperative that researchers keep respondents' identities confidential. To ensure confidentiality, researchers should not link respondents' identifiers to their survey responses when using data. Common identifiers include names, social security numbers, addresses, and telephone numbers.
Anonymity is an even stronger safeguard of respondent privacy. If a researcher assures anonymity, it means that the researcher is unable to link respondents' names to their surveys.
Advantages and Disadvantages of Survey Research
Sample surveys are a cost-effective and efficient means of gathering information about a population. Survey sampling makes it possible to accurately estimate the characteristics of a target population without interviewing all members of the population. Survey sampling is particularly useful when the population of interest is very large or dispersed across a large geographic area.
Surveys do not allow researchers to develop an intimate understanding of individual circumstances or the local culture that may be the root cause of respondent behavior. Respondents often will not share sensitive information in the survey format. A growing problem in survey research is the widespread decline in response rates.