sampling frames

2.    Name some possible sampling frames for the following:

a.    Electric contractors

A possible sampling frame might be obtained from a mailing list broker or membership list of a professional organization.

b.    Tennis players

Obtaining a list of tennis players may be difficult.  It may be possible to obtain a list of people who subscribe to Tennis magazine.  This list will tend to be a list

of “better than average” or regular players rather than including many beginners or powderpuff players.  Systematic sampling at tennis clubs and city courts may be

another alternative if personal interviews can be utilized; however, these will also be influenced by sampling frame error.

c.    Dog owners

A list of dog owners may possibly be obtained from a list of individuals who have sent in a “coupon” for a dog product, or possibly obtained from a consumer panel that

prescreens subjects with respect to certain demographic questions and ownership questions.  In towns where owners must purchase a license, the city government may also

be a source of names.

d.     Foreign-car owners

This may be obtained from automobile registrations.

e.    Wig and hair goods retailers

This may be obtained from a mailing list broker.

f.    Minority-owned businesses

Most states have some record of minority-owned businesses.

g.    Men over six feet tall

This information may be obtained from driver’s license files in various states.

4.    In what type of situation is conducting a census more appropriate than sampling?  When is sampling more appropriate than taking a census?

Of course, a researcher investigating a population with an extremely small number of population elements may elect to conduct a census rather than a sample because the

cost, manpower, and time drawbacks are relatively insignificant.  Thus, a company concerned with programmer satisfaction with its personal computer networking system

may not have any pragmatic reason for avoiding in-house circulation of a questionnaire to all 25 of its employees.  However, in most situations there are many

pragmatic reasons for sampling, especially cost, resource, and time advantages.  Further, sampling can be very accurate, and in some cases more accurate than a census.

5.    Comment on the following sampling designs:

a.    A citizen’s group interested in generating public and financial support for a new university basketball arena prints a questionnaire in area

newspapers.  Readers return the questionnaires by mail.

Those most interested in basketball or those most opposed to the financial program will be most likely to spot the questionnaire and return it.  This method of self-

selection will probably cause the sample to bias toward the two extreme groups.

b.    A department store that wishes to examine whether the store is losing or gaining customers draws a sample from its list of credit card holders by

selecting every tenth name.

While the idea of selecting every 10th name in a systematic fashion is fine, it must be questioned whether or not the credit card customers are representative of all

of the store’s customers.  If not, there will be a problem with this method of sampling.

c.    A motorcycle manufacturer decided to research consumer characteristics by sending one hundred questionnaires to each of its dealers.  The dealers would

then use their sales records to track down buyers of this brand of motorcycle and distribute the questionnaires.

This is a poor sampling technique.  The manufacturer has delegated the responsibility of sampling to dealers who may not know anything at all about research.  Some

dealers may have very accurate sales records and utilize some random process for generating 100 names.  However, it is likely that some dealers would select the first

100 names or the 100 best customers or some other convenient method.

d.    An advertising executive suggests that advertising effectiveness be tested in the real world.  A one-page ad is placed in a magazine.  One-half of the

space is used for ad itself.  On the other half, a short questionnaire requests that readers comment on the ad.  An incentive will be given for the first thousand


This is a poor sampling design.  First, only those individuals who notice the ad can be in the sample.  Thus, the sample is highly biased.  Second, only those who

“self-select” to respond are in the sample, which biases the results even more.

e.    A research company obtains a sample for a focus group through organized groups such as church groups, clubs, and schools.  The organizations are paid

for securing respondents; no individual is directly compensated.

This technique is often used.  It is convenient for the researchers because it often generates a group session where conversation will be lively.  However, if the

church groups, clubs, etc. are unrepresentative of the population, this technique should not be used.  For example, a group having fewer working women than the

population at large may not be representative.

f.    A researcher suggests replacing a consumer diary panel with a sample of customers who regularly shop at a supermarket that uses optical scanning

equipment.  The burden of recording purchases by humans will be replaced by computerized longitudinal data.

There may be several flaws and biases resulting from a panel where shoppers are strictly single-store shoppers.  Single-store shoppers may be less deal-prone than

other shoppers, and they may be less prone to buy private label merchandise.

g.    A banner ad on a business-oriented Web site reads, “Are you a large company Sr. Executive? Qualified execs receive $50 for under 10 minutes of time.

Take the survey now!” Is this an appropriate way to select a sample of business executives?

Business executives are a hard to reach population.  This site clearly will not yield a probability sample. However, it may be a cost-effective way to conduct an

Internet survey with executives. Alternatives are sampling services that sell mailing lists or databases of names.

8.    If researchers know that consumers in various geographical regions respond quite differently to a product category, such as tomato sauce, is area sampling

appropriate?  Why or why not?

In area sampling, the sampling unit is no longer the individual element in the population but the geographical area.  If one geographical area is unusual, it is

possible that the entire sample results could be distorted when that particular area is selected.  Ideally the geographical area selected is as heterogeneous as the

population itself—a mirror image of the population.

10.    What geographical units within a metropolitan area are useful for sampling?

There are numerous geographical units that are useful in sampling.  The census tract, the census block, Zip Codes, Zip Codes + 4, and many others.

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