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Chapter XII

Chapter XII. Sampling: Final and Initial Sample Size Determination. Chapter Outline 1) Overview 2) Definitions and Symbols 3) The Sampling Distribution 4) Statistical approaches to Determining Sample Size 5) Confidence Intervals i. Sample Size Determination: Means

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Chapter XII

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  1. Chapter XII Sampling: Final and Initial Sample Size Determination

  2. Chapter Outline 1) Overview 2) Definitions and Symbols 3) The Sampling Distribution 4) Statistical approaches to Determining Sample Size 5) Confidence Intervals i. Sample Size Determination: Means ii. Sample Size Determination: Proportions 6) Multiple Characteristics and Parameters 7) Other Probability Sampling Techniques

  3. 8) Adjusting the Statistically Determined Sample Size 9) Non-response Issues in Sampling i. Improving the Response Rates ii. Adjusting for Non-response 10) International Marketing Research 11) Ethics in Marketing Research 12) Internet and Computer Applications 13) Focus On Burke 14) Summary 15) Key Terms and Concepts 16) Acronyms

  4. Symbols for Population and Sample Variables Table 12.1 - - - - -

  5. _ _ _ XL X XU 95% Confidence Interval Figure 12.1 0.475 0.475

  6. Sample Size Determination for Means and Proportions Table 12.2 - -

  7. Sample Size For Estimating Multiple Parameters Table 12.3

  8. Methods of Improving Response Rates Reducing Refusals Reducing Not-at-Homes Callbacks Improving Response Rates Fig. 12.2 Questionnaire Design and Administration Follow-Up Other Facilitators Prior Notification Motivating Respondents Incentives

  9. Arbitron Responds to Low Response Rates RIP 12.1 Arbitron, a major marketing research supplier, was trying to improve response rates in order to get more meaningful results from its surveys. Arbitron created a special cross-functional team of employees to work on the response rate problem. Their method was named the “breakthrough method” and the whole Arbitron system concerning the response rates was put in question and changed. The team suggested six major strategies for improving response rates: 1. Maximize the effectiveness of placement/follow-up calls. 2. Make materials more appealing and easy to complete. 3. Increase Arbitron name awareness. 4. Improve survey participant rewards. 5. Optimize the arrival of respondent materials. 6. Increase usability of returned diaries. Eighty initiatives were launched to implement these six strategies. As a result, response rates improved significantly. However, in spite of those encouraging results, people at Arbitron remain very cautious. They know that they are not done yet and that it is an everyday fight to keep those response rates high.

  10. Exit Polling of Voters RIP 12.2 Warren Mitofsky, executive director of Voter Research and Surveys (VRS), states that planning exit interviews for a presidential election begins two years before the big day. The New York City-based staff of 22 grows to 60 during an election year; on election day, it blossoms to 6,000 workers who conduct exit interviews at 1,500 polling places. VRS workers give voters a list of about 25 questions. Certain issues are well-known determinants of a voter’s choice, whereas other questions deal with last-minute events such as political scandals. The questions are written at the last possible moment. The questionnaire is designed to determine not onlyfor whom people voted but on what basis.

  11. RIP 12.2 Contd. Uncooperative pollsters are a problem among exit polling. VRS workers are told to record a basic demographic profile for non-compliers. From this demographic data, a voter profile is developed to replace the uncooperative pollster using the method of substitution. Age, sex, race, and residence are strong indicators of how Americans vote. For example, younger voters are more likely to be swayed by moral issues whereas older voters are more likely to consider a candidate’s personal qualities. Thus, VRS substitutes for non-respondents for other potential respondents who are similar in age, sex, race, and residence. The broad coverage of exit interviews and the substitution technique for non-compliant pollsters allow VRS to obtain margins of error close to 3 to 4%.

  12. Use of Trend Analysis in Adjusting for Non-response Table 12.4

  13. Finding Probabilities Corresponding to Known Values Figure 12A.1 Area is 0.3413 Z Scale

  14. Finding Values Corresponding to Known Probabilities Figure 12A.2 Area is 0.500 Area is 0.450 Area is 0.050 X Scale X 50 Z Scale -Z 0

  15. Area is 0.025 Finding Values Corresponding to Known Probabilities: Confidence Interval Fig. 12A.3 Area is 0.475 Area is 0.475 Area is 0.025 X Scale X 50 Z Scale -Z -Z 0

  16. Opinion Place Bases Its Opinions on 1000 Respondents RIP 12.3 Marketing research firms are now turning to the Web to conduct online research. Recently, four leading market research companies (ASI Market Research, Custom Research Inc., M/A/R/C Research and Roper Search Worldwide) partnered with Digital Marketing Services (DMS), Dallas, to conduct custom research on AOL. DMS and AOL will conduct online surveys on AOL's Opinion Place, with an average base of 1,000 respondents by survey. This sample size was determined based on statistical considerations as well as sample sizes used in similar research conducted by traditional methods. AOL will give rewards points (that can be traded in for prizes) to respondents. Users will not have to submit their e-mail addresses. The surveys will help measure response to advertiser's online campaigns. The primary objective of these researches is to gauge consumers' attitudes and other subjective information that can help media buyers plan their campaigns.

  17. RIP 12.3 Contd. Another advantage of online surveys is that you are sure to reach your target (sample control) and that they are quicker to turn around than traditional surveys like mall intercepts or home interviews. They also are cheaper (DMS charges $20,000 for an online survey, while it costs between $30,000 and $40,000 to conduct a mall-intercept survey of 1,000 respondents).

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