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Lecture Marketing research - Chapter 11: Sample size determination

In this chapter, students will be able to: Learn the financial and statistical issues in the determination of sample size, discover the methods for determining sample size, gain an appreciation of a normal distribution, understand population, sample, and sampling distribution, distinguish between point and interval estimates, recognize problems involving sampling means and proportions. | Copyright © 2004 John Wiley & Sons, Inc. Sample Size Determination CHAPTER Eleven Learning Objectives 1. To learn the financial and statistical issues in the determination of sample size. 2. To discover the methods for determining sample size. 3. To gain an appreciation of a normal distribution. 4. To understand population, sample, and sampling distribution. Learning Objectives 5. To distinguish between point and interval estimates. 6. To recognize problems involving sampling means and proportions. Financial, Statistical, and Managerial Issues As a general rule: The larger the sample, the smaller the sampling error. Larger samples cost more; however the sampling error decreases at a rate equal to the square root of the relative increase in sample size. Before trying to determine the size of the sample, the confidence intervals need to be decided. The financial and statistical issues in the determination of sample size. Determining Sample Size for Probability Samples Budget Available Sample Size—a project is often determined by the available budget Alternative Data Collection Approaches—budget constraints force the researcher to explore and consider the value of information in relation to its cost The financial and statistical issues in the determination of sample size. Methods for Determining Sample Size Rules of Thumb - Desired sampling error - Similar Studies - Past experience - A gut feeling Number of Subgroups To Be Analyzed The sample should contain at least 100 respondents in each major subgroup. Traditional Statistical Methods An estimate of the population standard deviation. The acceptable level of sampling error. The desired level of confidence that the sample will fall within a certain range of the true population values. To discover the methods for determining sample size. Methods for Determining Sample Size General Properties for the Normal Distribution Crucial to Classical Statistical Inference Reasons For Its Importance Many variables have probability | Copyright © 2004 John Wiley & Sons, Inc. Sample Size Determination CHAPTER Eleven Learning Objectives 1. To learn the financial and statistical issues in the determination of sample size. 2. To discover the methods for determining sample size. 3. To gain an appreciation of a normal distribution. 4. To understand population, sample, and sampling distribution. Learning Objectives 5. To distinguish between point and interval estimates. 6. To recognize problems involving sampling means and proportions. Financial, Statistical, and Managerial Issues As a general rule: The larger the sample, the smaller the sampling error. Larger samples cost more; however the sampling error decreases at a rate equal to the square root of the relative increase in sample size. Before trying to determine the size of the sample, the confidence intervals need to be decided. The financial and statistical issues in the determination of sample size. Determining Sample Size for Probability Samples Budget Available .