On a regular spring time a lot of tulip flower fields outside the Keukenhof are headed (taking the flower off) on the 30th of April or within a couple of days after it. If you want to see the flower fields as well make sure that you visit before this date!
In factorial designs, a factor is a major independent variable. In this example we have two factors: time in instruction and setting. A level is a subdivision of a factor. In this example, time in instruction has two levels and setting has two levels. Sometimes we depict a factorial design with a numbering notation.
A cross-sectional study design is used when. 1  The purpose of the study is descriptive, often in the form of a survey.  The purpose of the study is to find the prevalence of the outcome of interest, for the population or subgroups within the population at a given timepoint.