• Proceedings of the Korean Statistical Society Conference
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• 2005.11a
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• pp.79-84
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• 2005

The growing number of households with only cellular phones and no landline telephones, is decreasing the coverage of the landline frame. Dual frame sample designs are considered which draw phone numbers from the landline and the cellular number frame. Cellular phones may be used as personal or household devices. Weighting strategies appropriate to compensate for unequal probabilities in selecting dual frame samples are proposed. Also, some current issues are discussed.

• Asian Journal for Public Opinion Research
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• v.1 no.1
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• pp.26-41
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• 2013

The rise and fall of social research methods rely on how much a certain method is able to appropriately reflect the change of society. The present research proposes new mobile surveying methods, considering the current and future trends in Korea. In particular, this research focuses on environmental pressure (time constraints, the presence of others and the place) as one of the major factors influencing the effects of survey modes. For example, landline surveys are conducted in the respondent's home, which is a private and fixed space. On the other hand, surveys on mobile phones can be conducted in diverse places with other people around. After sampling 500 landline respondents and 500 mobile phone respondents using a quota method, the same questionnaire was used for both the mobile and landline interviews. The findings are generally consistent with the literature supporting the data quality and comparability of the mixed mode survey. These results are encouraging for researchers designing surveys that feature mobile phone data collection.

• Survey Research
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• v.10 no.1
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• pp.33-56
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• 2009

Landline telephone surveys of the population of households or individuals in Korea often use telephone directories as sampling frames. Recently, the frequency of unlisted numbers in the directories has been increased and the number of households without landline phones has become larger with a spread of mobile phones. Landline telephone coverage has currently reached to a level that raises concerns about the currently due to a coverage bias on the statistics in question. In this paper, we first present the distribution of telephone ownership in Korea and make a comparison with some selected countries. Second, we describe the characteristics of telephone directories. Next, we directly or indirectly estimate the telephone coverage rates of the frames, and show that it may nationally be lower than 65.6% based on additional information. We conclude with remarks about future studies to reduce coverage bias, including the developments of efficient random digit dialing sampling methods.

• Survey Research
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• v.13 no.1
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• pp.135-158
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• 2012

Korean telephone surveys have been based on landline telephone directory or RDD(Random Digit Dialing) method. These days, however, there has been an increase of the households with no landline, or households with the line but not willing to register in the directory. Moreover, it is hard to contact young people or office workers who are usually staying out of home in the daytime. Due to these issues above, the predictability of election polls gets weaker. Especially, low accessibility to those who stay out of home when the poll's done, results in predictions with positive inclination toward conservatism. A solution to resolve this problem is to contact respondents by using both mobile and landline phones-via landline phone to those who are at home and via mobile phone to those who are out of home in the daytime(Mixed Mode Survey, hereafter MMS). To conduct MMS, 1) we need to obtain the sampling frames for the landline and mobile surveys, and 2) we need to decide the proportion of sample size of both. In this paper, we propose a heuristic method for conducting MMS. The method uses RDD for the landline phone survey, and the access panel list for the mobile phone survey. The proportion of sample sizes between landline and mobile phones are determined based on the 'Lifestyle and Time Use Study' conducted by Statistics Korea. As a case study, 4 election polls were conducted in the periods of the special election for the mayor of Seoul on Oct 26th, 2011. From the initial 3 polls, reactions and responses regarding the issues raised during the survey period were appropriately covered, and the final poll showed a very close prediction to the real election result.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.299-302
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• 2011

Recently, Voice over Internet protocol(VoIP) in IP-based wired and wireless voice, as well as by providing multimedia information transfer. Wired and wireless VoIP is easy on illegal eavesdropping of phone calls and VoIP call control signals on the network. In addition, service misuse attacks, denial of service attacks can be targeted as compared to traditional landline phones, there are several security vulnerabilities. In this paper, VoIP equipment in order to obtain information on the IP Phone is scanning. And check the password of IP Phone, and log in successful from the administrator's page. Then after reaching the page VoIP IP Phone Administrator Settings screen, phone number, port number, certification number, is changed. In addition, IP Phones that are registered in the administrator page of the call records check and personal information is the study of hacking.