# Knowledge and Consumption Habits Related with White Crowberries (_Corema album_ L.)
## 2 Materials and Methods  
### Instrument and Data Collection  
The instrument used for this research was a questionnaire (Supplementary Material S1) which was prepared specifically for this purpose. It included 6 different parts, namely:  
Figure 1: Endemic shrub of Atlantic coastal dunes of Iberian Peninsula: (**a**) _Corema album_ (L.) D. Don (Ericaceae) shrub and (**b**) its small fruits (Portuguese white crowberries) in a traditional basket.  
(I) Sociodemographic variables (8 questions); (II) Knowledge about crowdberries (2 questions, 8 items); (III) Consumption habits (5 questions); (IV) Knowledge about their nutritional composition and health effects (1 question, 10 items); (V) Social aspects related to this fruit (3 questions, 10 items).  
The survey was conducted on a convenience sample, based on the facility of recruitment and willingness to answer the questionnaire. Although some limitations can be pointed out to the use of convenience samples, they also have some positive aspects and are eligible for exploratory research [18; 19]. The sample size was calculated based on some principles, namely a 95% confidence interval, corresponding to a level of significance of 5% and a z score of 1.96. The power of the test considered corresponds to an error of 5%, which corresponds to a minimum acceptable probability of preventing type II error equal to 0.05 [20; 21]. The Portuguese population in 2019 (the last year available) was 10,283 thousand people, of which about 80% are adults, aged 18 years old or over [22]. Considering a target population of 50% of the Portuguese adults, the sample size was calculated as 385 participants [23; 24; 25]. Hence, a minimum of 385 participants should be used to take this survey as representative and with statistical relevance. The data were collected through an internet platform and the request to fill the questionnaire was sent by different internet tools, such as email and social networks. Only participants 18 years old or more were included in the study, and other inclusion criteria were having access to internet, having a computer or other devices through which they could answer the questionnaire, being able to understand the questions and express their responses, and willingness to participate in the research voluntarily and anonymously. The participation had to express their informed consent to participate in the study, and they could only access the questionnaire after confirming the participation. Additionally, it was guaranteed that the internet tool used for the questionnaire did not record any data from the participants, like email, IP or others. All ethical issues were respected when designing and applying the questionnaire, which was approved by the Ethical Commission at the Polytechnic Institute of Viseu with reference 22/SUB/2021.  
The number of responses received was 520, however, some had to be rejected due to some excluding criteria. Fourteen were rejected because the participants' age was under 18 years old (between 12 and 17 years), although having agreed to be adults in order to access the questionnaire. Another 5 participants were excluded for not residing in Portugal (one in the United States, one in France, one in Sweden, one in Mozambique and one did not declare where he lived). Hence, the final number of valid responses considered for the study was 501, which was higher than the minimum number of 385 calculated based on the above mentioned assumptions. These answers were obtained from Portuguese citizens from the following municipalities, which cover almost the entire Portuguese territory: Azores, Aveiro, Beja, Braga, Braganca, Castelo Branco, Coimbra, Evora, Faro, Guarda, Leiria, Lisbon, Portalegre, Porto, Santarem, Setubal, Viana do Castelo and Viseu.