Which of the options best fits gap 11?

Directions: Fill in the gaps to form meaningful sentences in the following passage.

A sample design is a definite plan determined before any data -------8---collected for obtaining a sample ------9-----a given population. Samples can either be probability samples ------10-------non- probability samples. With probability samples, each element ------11-----a known probability of being included in the sample but the non - probability samples -------12-----allow the researcher to determine this probability. The sample design to be used ------13-----decided by the researcher taking into consideration the nature of the enquiry.