management assignment

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Kong MGM 403

Sampling III

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Kong MGM 403

Sampling Error and Nonsampling Error Revisit

• Total error is difference between sample statistics and the corresponding population value

• Total Error = Sampling Error + Nonsampling Error

Population Sample

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Kong MGM 403

Nonsampling Error

• Also called “systematic” error; persists as sample size increases

• Nonresponse error: nonrespondents systematically different from respondents in a way that affect the key study variables – E.g., estimating percent of population exhibiting

depression symptoms

• Self-selection bias: people who feel strongly about a subject are more likely to respond to survey

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Kong MGM 403

Nonsampling Error

• Sample selection error (caused by improper sampling design, screening criteria, sampling procedure execution) – E.g., stopping respondents during daytime hours

in shopping centers excludes working people

– Using web intercept (pop-up windows) under- samples infrequent internet users

• Sampling frame error: sampling frame different from target population

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Kong MGM 403

Case Example: Survey for New Greek Yogurt Launch

• Survey Description: – Questions: elicited preferences for new GY

products not observed in the market by choosing among GY options

– Population: All shoppers of the retailer

– Sample Frame: Loyalty Card Users

– Screening Criteria: Must buy GY in last 6 months

– Sample Size: approximately 700

• What do you think were main source of nonsampling error here?

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Case Example: MBA’s May Be A Marketing Liability

MBA’s May Be A Marketing Liability… “A master of Business Administration degree is not only worthless, it can work against a marketer, according to a survey of marketing executives from 32 consumer-products companies by consulting firm Ken Coogan & Partners...Marketing executives from 18 underperforming companies – which had sales grow 7% less than their categories on average in the last two years ended August 2005 – were twice as likely to have been recruited out of MBA programs than marketing executives from out-performing companies, which averaged growth 6.2% faster than their categories over the two years.”

Source: AdAge.com, March 21, 2006

Mktg. Executive had an MBA

Mktg. Executive did not have an MBA

Overperformers (n = 9) 55.5% 44.5%

Underperformers (n = 18) 88.9% 11.1%

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Kong MGM 403

• Read “What’s behind the numbers?” (course pack) first two sections “Before you base big decisions on survey results… ” and “Sample with care”; about 1.5 pages