Answer:
Explanation:
In statistics, whenever full population cannot be surveyed, a random sample can be taken and from the observations population behaviour can be estimated.
Here given that there are 200 members. Instead of collecting data from all 200, 20 members are randomly taken.
The sample mean x bar can be estimated to give an idea the population mean also.
ACcording to central value theorem, means of different samples will follow a distribution with mean = population mean and std deviation = std dev of sample/square root of n
Hence we fix confidence interval as Mean + or - Z critical * std error
This gives us an idea about within which means will lie for different samples and hence give an idea about population mean also.