The North China plain is a flatness which has been formed by the time with the sediments of the Yellow river.
As it was not uploaded an image to indicate where this plain is, a picture from google was chosen for this purpose giving some directions on a map of China.
Overloaded to work with a specific class
Answer: the 15th ammendment
A-B-A-B design could provide the most valid non intervention measure with demonstration of experimental control.
In statistics, the experimental design, also known as the design of experiment (DOE), is described as the layout of an information-gathering experiment in which a variation may or may not be present. Typically, controlled experiments use this phrase. In order to make the results more reliable, these tests minimize the impacts of the variable. In this design, a group of people, plants, animals, etc. may participate in an experimental unit's procedure.
Pre-experimental research designs are the most straightforward kind of experimental research designs in statistics. Following the identification of some factors as causes and effects, a group or groups are kept under observation in this method. Typically, this approach is used to determine whether the targeted group need additional research. This is the reason why this procedure is regarded as being economical.
Learn more about experimental control here
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