When a random observations are selected from a number of individual groups in a particular population, the type of sampling technique is called Stratified Random sampling. Stratified Random sampling begins with the partitioning or splitting or a population into subgroups. A number of random selection are then made from each of the subgroups to form a collection of larger samples. This is different from the simple random sampling technique which makes random selection directly from a larger sample or population without prior partitioning of the population. The different grades of students represents the individual stratum from which random selections are made.
The sum of the interior angles of a triangle is always 180 degrees. The exterior angle is the angle between any side of a shape, and a line extended from the next side. The sum of an exterior angle and its adjacent interior angle is also 180 degrees.
