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Sample size is the act of determining the number of samples or replicates to include in the statistical sample.

The important feature of this is to make inferences in the population of the sample.

It is based on the expenses of the data collection and plays a vital role to determine statical power.

The important feature of this is to make inferences in the population of the sample.

It is based on the expenses of the data collection and plays a vital role to determine statical power.

Sample size is a number of observation

n = $\left ( \frac{\sigma z}{E} \right )^{2}$

Non-Statistical or Non-probability sampling is a sampling procedure, which does not have any probability involved in it. All the items selected will be purposely selected for some reason.

(1) Convenience Sampling

(2) Quota Sampling

(3) Judgment samplingThe non-statistical sampling methods are sometimes known as restricted sampling

Based on the method of sampling and some basic factors, we have to select the sample size.

There are many factors affecting the size of the sample

- The sample size depends on the budget of the survey. For a big budget survey we can opt for a bigger sample size
- It depends on the complexity of the design. If the design is more complex, we will select a bigger sample
- Sample size will depend upon the level of precision required
- It depends upon the method of sampling used
- It depends on the spread of the data in the population

Sample size determination

It is the method of selecting the appropriate sample from the population. It suggests how many items are to be included in the sample.

How to determine sample size

There are mainly two different methods of selecting a sample. They are : -

(1) Simple Random sampling

(2) Stratified Sampling

(3) Systematic SamplingThe statistical sampling methods are sometimes known as unrestricted sampling.

a) Confidence level (1- $\alpha$) %

b) Margin of error E

c) Standard deviation of the population $\sigma$

When we know the above values, the appropriate sample size n is given by

n = $\left ( \frac{\sigma z}{E} \right )^{2}$where z is obtained from the standard normal tables.

d) Confidence level (1- $\alpha$) %

e) Margin of error E

f) True proportion of success p

When we know the above values, the appropriate sample size n is given by

n = $\left ( \frac{z}{E} \right )^{2}$ p(1-p)where z is obtained from the standard normal tables.