A sample is any subset of the total population. A representative sample is one that is chosen so that its characteristics are similar to that of the population.
That the key characteristics of the population are reflected in the sample.
A simple random sample.
It is called a representative sample.
To generalize results from the sample population to the target population.
A sample is any subset of the total population. A representative sample is one that is chosen so that its characteristics are similar to that of the population.
That the key characteristics of the population are reflected in the sample.
Many statistical statements for a population which are based on a sample are not valid if the sample is not representative.
A representative sample is one where the statistics of the sample are the same as the statistics for the parent population.
If the sample is not representative of the population, then the characteristics of the sample are not the characteristics of the population. Example: If I want to estimate the percentage of the population that are men, and my sample is the school's football team, my estimate would be that 100% of the population is comprised of men. What went wrong with my survey ? Simple. The football team is not a representative sample of the population, at least not as regards gender.
A simple random sample.
It is called a representative sample.
A sample that accurately reflects the characteristics of the population as a whole
.representative
It is important for a sample to be representative, so that the whole population's view is counted, and not biased by one particular group within the population.
If measurements are taken for two (or more) variable for a sample , then the correlation between the variables are the sample correlation. If the sample is representative then the sample correlation will be a good estimate of the true population correlation.
The relations depend on what measures. The sample mean is an unbiased estimate for the population mean, with maximum likelihood. The sample maximum is a lower bound for the population maximum.