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EMR 6500: Survey Research. Dr. Chris L. S. Coryn Kristin A. Hobson Spring 2013. Agenda. Simple random sampling Crafting good questions Midterm examination Case Study #1 Case Study #2. Simple Random Sampling. Simple Random Sample.
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EMR 6500:Survey Research Dr. Chris L. S. Coryn Kristin A. Hobson Spring 2013
Agenda Simple random sampling Crafting good questions Midterm examination Case Study #1 Case Study #2
Simple Random Sample Recall that a simple random sample is a sample of n elements from a population of N in which each possible sample of size n has the same probability of selection, namely The probability of any element being selected is equal to the ratio of the sample size to the population size
Example for a Population Mean If n = 200 was selected from N = 1,000 and the sample mean was = 94.22 with a sample variance of = 445.21, the bound on the error of estimation, B, would be
Example for a Population Total If n = 50 was selected from N = 750 and the sample mean was = 10.31 ( = 750(10.31) = 7,732.5) with a sample variance of = 2.25, the bound on the error of estimation, B, would be
Selecting the Sample Size for Estimating Population Means and Totals
Sample Size for Estimating Population Means Often, the population variance, , is unknown An approximate value of can be obtained by
Example for a Population Mean If N = 1,000 and the estimated range is 100, the sample size necessary to estimate with B = 3 would be and
Example for a Population Mean If where then
Sample Size for Estimating Population Totals If N = 1,000 and = 36.00, the sample size necessary to estimate the population total, , with B = 1,000 would be then
Example for a Population Proportion If n = 100 was selected from N = 300 and the sample proportion was = 0.15 the bound on the error of estimation, B, would be
Selecting the Sample Size for Estimating a Population Proportion
Example for a Population Proportion If N = 2,000 and the desired bound on the error of estimation, B, were 0.05, and no prior information is available to estimate , the necessary sample size would be
Issues to Consider What survey mode(s) will be used to ask the questions? Is the question being repeated from another survey, and/or will answers be compared to previously collected data? Will respondents be willing and motivated to answer accurately? What type of information is the question asking for?
Choosing Words and Forming Question • Make sure the question applies to the respondent • Make sure the question is technically accurate • Ask one question at a time • Use simple and familiar words • Use specific and concrete words to specify the concepts clearly • Use as few words as possible to pose the question • Use complete sentences with simple sentence structures • Make sure “yes” means yes and “no” means no • Be sure the question specifies the response task
Visual Presentation of Survey Questions Use darker and/or larger print for the question and lighter and/or smaller print for answer choices and answer spaces Use spacing to create subgrouping within a question Visually standardize all answer spaces or response options Use visual design properties to emphasize elements that are important to the respondent and to deemphasize those that are not Make sure words and visual elements that make up the question send consistent messages Integrate special instructions into the question where they will be used rather than including them as freestanding entities Separate optional or occasionally needed instructions from the question stem by font or symbol variation Organize each question in a way that minimizes the need to reread portions in order to comprehend the response task Choose line spacing, font, and text size to ensure the legibility of the text
Additional Considerations • Abilities/aptitudes • Knowledge or skill • Attitudes • General and enduring evaluation of a person, object, or concept • Behaviors • Actions and mannerisms • Opinions/beliefs • Subjective beliefs that occur as a result of emotion or interpretation of facts
Guttman Scaling Individuals who endorse the first response should also endorse all others as they represent less extreme views
Midterm Examination • The examination will consist of 50-75 multiple-choice items, scored as 0 or 1 • You will have 2½ hours to complete the examination • You may use one page of notes (front and back) on 8½” X 11’’ paper • You will be required to determine necessary sample sizes and calculate bounds on the error of estimation for means, totals, and proportions • You may use a calculator or an Excel spreadsheet on a laptop computer • You cannot use the internet or textbooks
Case Study Activity • Write a focal question that addresses what proportion of foundations formally assess the effectiveness of their grant making activities • Determine the motivational features that you would use to encourage high quantity and quality of responses, with particular attention to: • How the perceived rewards for responding would be increased • How the perceived costs of responding would be reduced • How trust would be established so that people believe the rewards will outweigh the costs of responding • Determine the necessary sample size to estimate the population proportion, p, of foundations (N = 888) to address your focal question with a bound on the error of estimation of B= 0.05 and B = 0.10
Case Study Activity • Consider the guidelines for “choosing words and framing questions” and “visual presentation of survey questions” • Are there any errors associated with the guidelines for choosing words and framing questions? • Are there any errors associated with the guidelines of the visual presentation of survey questions?
