Why are techniques like cluster sampling and multistage sampling just as externally valid as simple random sampling?

Due to the fact that they all contain elements of random selection, techniques like cluster sampling and multistage sampling are just as externally valid as simple random sampling due to the fact that they all contain elements of random selection.

Cluster sampling are more or less alike, each heterogeneous and resembling the overall population. The population is split into representative clusters, then a selection is done one or few from the clusters, then lastly, a census is performed with those selected clusters.

In multistage sampling, several methods are combined in sampling schemes and occasionally utilized the same method or different methods or more than once. Though they have different steps in being done, they both have random selection elements. 

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step-by-step explanation:

exa:

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3+11

14

step-by-step explanation:

from this example, we can see that subtracting with integers is the same as adding the opposite. we can solve using a number line or by using the saying "keep, change, change" to us solve. it is important to remember that we can subtract a negative and end up with a larger number than we started with.