The sampling design, performance criteria of the sampling and associated optimal sample size were obtained by statistical analysis of soil data available before the sampling.
In conventional sampling, the sampling design is based entirely on a priori information, and is fixed before the study begins.
Eventually, the data used for supporting the sampling design can be retrieved after collecting answers with a measurement instrument such as a characterization form, before executing the survey.
First, the sample design used is not representative, and therefore we need caution before generalizing our results.
The basic sampling design is simple random sampling, based on probability theory.
Data were analysed based on the NIS sampling design.
A Before, After, Control Impact (BACI) sampling design was followed and the results of abiotic and biological variables were compared between treatment site (control, pens, and two areas at 15 and 50 m from the pens) and timing (before shrimp addition, during culture and after harvest), through ANOVA.
That said, several questions had been successfully used before, and the sampling was designed to reach people with a range of characteristics, particularly older age groups which were not surveyed in previous Natsal studies and those with multiple recent partners.
Density data from beneath the cage and the three control sites was analysed within a beyond-B.A.C.I. (Before-After, Control-Impact) with asymmetrical sampling design, while a Before-After approach was used to analyse data from other sites.
The fundamental importance of Sampling Design and of instrument validation before and after the monitoring campaign was enhanced.
