random sampling ,systematic sampling , self-selected , and there is one more i don't know
There is no sampling method that will select the exact population.
Non probability sampling and probability sampling are different because probability sampling uses random samples. Non probability sampling aren't random, but can still be representative of the population as a whole if done correctly.
The only way to get rid of sampling error is to use the entire population under study. This is usually impossible, so the next best thing is to use large samples and good sampling methods.
Name and describe three methods of scientific statistical samplingRead more: Answers.com
There are many such methods: cluster sampling, stratified random sampling, simple random sampling.Their usefulness depends on the circumstances.
Quota sampling stratified sampling random sampling convenient sampling cluster sampling semi stratified sampling stratified quota
chemicals
random sampling ,systematic sampling , self-selected , and there is one more i don't know
Soil sampling
Samples for what? If you are sampling for the basic test that most extension offices perform, it doesn't matter.
There is no sampling method that will select the exact population.
On this website, http://www.ams-samplers.com/category.cfm?CNum=1, there are several different types of soil sampling equipment and they all range in price. They have sampling kits, and equipment for the more advanced farmers.
Non probability sampling and probability sampling are different because probability sampling uses random samples. Non probability sampling aren't random, but can still be representative of the population as a whole if done correctly.
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Amniocentesis and chorionic villi sampling.
basically it is cheaper than other methods so it is preferred over other methods.