Gli intervistatori vengono istruiti mediante briefing scritto e seguiti costantemente con contatti telefonici.
Le interviste di SinOmnibus vengono condotte personalmente, al domicilio della persona intervistata, a
seguito della selezione casuale sul territorio da punti di partenza assegnati; in caso di “caduta” (rifiuti,
interviste incomplete) l’individuo è sostituito secondo quota.

3 In particolare, sulla base di studi metodologici ormai consolidati e in virtù di una lunga esperienza di ricerca, è possibile affermare che qualsiasi tipo di field e di campionamento tenderà inevitabilmente a produrre campioni in cui la quota di individui con titoli di studio e/o professioni più elevate sarà maggiore di quella naturale”.

http://www.audimovie.it/Upload/continuativa nota metodologic...

Campioni non probabilistici
Campionamento per quote
E’ un campionamento stratificato
con scelta rimessa all’intervistatore
1. Si suddivide la popolazione in sottogruppi sulla base di
variabili di cui si conosce la distribuzione
2. Si determinano le quote del campione
3. All’interno di ciascuna quota, l’intervistatore è libero di
scegliere a sua discrezione i soggetti da intervistare

http://webhouse.unimc.it/economia/repo/fac_materiali/campion...


quota sampling
Hide links within definitionsShow links within definitions DefinitionA sampling method of gathering representative data from a group. As opposed to random sampling, quota sampling requires that representative individuals are chosen out of a specific sub-group. For example, a researcher might ask for a sample of 100 females, or 100 individuals between the ages of 20-30.
http://www.businessdictionary.com/definition/quota-sampling....

In quota sampling, the population is first segmented into mutually exclusive sub-groups, just as in stratified sampling. Then judgment is used to select the subjects or units from each segment based on a specified proportion. For example, an interviewer may be told to sample 200 females and 300 males between the age of 45 and 60. This means that individuals can put a demand on who they want to sample (targeting)

It is this second step which makes the technique one of non-probability sampling. In quota sampling, the selection of the sample is non-random unlike random sampling and can often be found unreliable. For example interviewers might be tempted to interview those people in the street who look most helpful, or may choose to use accidental sampling to question those which are closest to them, for time-keeping sake. The problem is that these samples may be biased because not everyone gets a chance of selection. This non-random element is its greatest weakness and quota versus probability has been a matter of controversy for many years.

Quota sampling is useful when time is limited, a sampling frame is not available, the research budget is very tight or when detailed accuracy is not important. You can also choose how many of each category is selected.

A quota sample is a convenience sample with an effort made to ensure a certain distribution of demographic variables. Subjects are recruited as they arrive and the researcher will assign them to demographic groups based on variables like age and gender. When the quota for a given demographic group is filled, the researcher will stop recruiting subjects from that particular group.

This is the non probability version of stratified sampling. Subsets are chosen and then either convenience or judgment sampling is used to choose people from each subset.

Stratified sampling is probably the most commonly used probability method. Subsets of the population are created so that each subset has a common characteristic, such as gender. Random sampling chooses a number of subjects from each subset.
http://en.wikipedia.org/wiki/Quota_sampling

http://www.google.com/#hl=en&q="according to quota sampling"...

Hi Tom,
I'm not an expert in market research, but I know statistics

Have a nice weekend :)

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Note added at 31 mins (2010-09-03 21:59:58 GMT)
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or:

according to quotas, as you please

Here it is Tom, although I am not at all sure it is right