Repeated participation in the survey . When conducting anonymous Internet research, there is a problem with establishing the fact of the uniqueness of a person's participation in a survey. Some respondents may take part in the study several times, having a significant impact on the final distribution of answers. The likelihood of this increases if there is material reward for participating in the study, or the survey participant is interested in distorting its results. For example, a fan of a football team, when asked which club will become the champion this year, may vote for his favorite club several times. In the same way, it is possible for the members of a musical group to vote repeatedly for themselves when conducting contests on the sites of radio stations.

Multiple email addresses allow the same person to fill out the questionnaire several times, disguising themselves as different names. Accordingly, it is necessary to identify the respondent, which prohibits the possibility of multiple responses to the questionnaire from the same computer.

To avoid repeated participation in the survey by the same people, identification of the IP-address of the computer from which the respondent logs in (in this case, however, respondents who can log in from the same IP-address “drop out” from the sample). Identification and control is carried out using special cookies.

Also, in addition to identifying the IP address, access to the electronic questionnaire is often organized using unique codes, passwords, etc. Although these measures are not always 100% effective (if you want to take the survey again, you can do it with computer or re-register under a different name and using a different password), however, they reduce the likelihood of re-participation in the study.

Lack of data on the general population. In most cases, there is no reliable data on the socio-demographic parameters of the general population - people who can potentially take part in the survey. For example, information about the participants of a certain forum or chat, among which a questionnaire can be sent. The probability of deliberate distortion of information is high. All data about himself (gender, age, education), the participant provides only if he considers it necessary. At the same time, deliberate misinformation is not excluded here, for example, the quite often practiced "gender reassignment". The task of data verification is extremely difficult.

Intentional corruption of data. It is difficult to assess the degree of reliability of the results obtained in the course of online research - the conscientiousness of filling out the questionnaire, the sincerity of the respondents, etc. The individual can give false or arbitrary answers to questions in order to have fun or see what happens.

Possibility of hostile actions. The software used to conduct Internet surveys may be susceptible to deliberate attack, “hacking” by computer hackers. This happens when a competing party is interested in distorting the research results or disrupting it. Most often, such "hacks" occur when conducting polls related to political or commercial topics, when one of the candidates or a certain brand is deliberately "accelerated" the rating.

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