Tham khảo tài liệu 'giáo trình marketing nghiên cứu - phần 13', kinh doanh - tiếp thị, tiếp thị - bán hàng phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Determining the Size of a Sample Sample Accuracy Sample accuracy: refers to how close a random sample’s statistic is to the true population’s value it represents Important points: Sample size is not related to representativeness Sample size is related to accuracy Ch 13 Sample Size and Accuracy Intuition: Which is more accurate: a large probability sample or a small probability sample? The larger a probability sample is, the more accurate it is (less sample error). Ch 13 A Picture Says 1,000 Words ± Probability sample accuracy (error) can be calculated with a simple formula, and expressed as a ± % number. n 550 - 2000 = 1,450 4% - 2% = ±2% Ch 13 How to Interpret Sample Accuracy From a report The sample is accurate ± 7% at the 95% level of confidence From a news article The accuracy of this survey is ± 7% Ch 13 How to Interpret Sample Accuracy Interpretation Finding: 60% are aware of our brand So between 53% (60%-7%) and 67% (60%+7%) of the entire population is . | Determining the Size of a Sample Sample Accuracy Sample accuracy: refers to how close a random sample’s statistic is to the true population’s value it represents Important points: Sample size is not related to representativeness Sample size is related to accuracy Ch 13 Sample Size and Accuracy Intuition: Which is more accurate: a large probability sample or a small probability sample? The larger a probability sample is, the more accurate it is (less sample error). Ch 13 A Picture Says 1,000 Words ± Probability sample accuracy (error) can be calculated with a simple formula, and expressed as a ± % number. n 550 - 2000 = 1,450 4% - 2% = ±2% Ch 13 How to Interpret Sample Accuracy From a report The sample is accurate ± 7% at the 95% level of confidence From a news article The accuracy of this survey is ± 7% Ch 13 How to Interpret Sample Accuracy Interpretation Finding: 60% are aware of our brand So between 53% (60%-7%) and 67% (60%+7%) of the entire population is aware of our brand Ch 13 Sample Size Axioms To properly understand how to determine sample size, it helps to understand the following axioms Ch 13 Sample Size Axioms The only perfectly accurate sample is a census. A probability sample will always have some inaccuracy (sample error). The larger a probability sample is, the more accurate it is (less sample error). Probability sample accuracy (error) can be calculated with a simple formula, and expressed as a +- % number. Ch 13 Sample Size Axioms You can take any finding in the survey, replicate the survey with the same probability sample size, and you will be “very likely” to find the same finding within the +- range of the original finding. In almost all cases, the accuracy (sample error) of a probability sample is independent of the size of the population. Ch 13 Sample Size Axioms A probability sample can be a very tiny percentage of the population size and still be very accurate (have little sample error). Ch 13 .
