The universe defined for the Survey on the Use of Postal Services was made up of individuals aged 15 years old or older, residing in Mainland Portugal or in the Autonomous Regions of Madeira or the Azores. In order to select the interviewees, the quota method was used with a view to gender, age, education level and professional occupation, while dwellings were previously selected by region and family size.
The table below details the characteristics of those surveyed and referenced in the body of this report:
|
|
Associated company |
Survey method |
Fieldwork |
Sample size |
Maximum margin of error (1) |
|
Dec. 2014 |
Nielsen |
Telephone (CATI) |
3 Nov to 3 Dec 2014 |
1,340 interviews |
2.68 |
|
Dec. 2012 |
GFK-Metris |
Telephone (CATI) |
8 Nov to 15 Dec 2012 |
1,374 interviews |
2.64 |
|
Dec. 2010 |
TNS-Euroteste |
Telephone (CATI) |
22 Nov to 22 Dec 2010 |
1,342 interviews |
2.68 |
(1) Absolute error margin or absolute precision (semi-range of a 95 percent confidence interval for a proportion) for questions directed at entire sample.
The results were rebalanced for the universe of individuals using weighting factors. The weighting factor was created in order to ensure that results reflected the socio-demographic structure of the Portuguese population aged 15 years old or over residing in the private households in Portugal. This process was based on the Census most recently conducted by INE (Statistics Portugal) prior to the fieldwork being performed.
