The Central Limit Theorem (CLT) is a fundamental concept in statistics that explains how the means of random samples from any population approach a normal distribution - irrespective of their underlying distributions.
CLT has great significance in inferential statistics as it allows us to make conclusions about the entire population, based on just a sample. It is also used across various fields like economics, engineering, social sciences and physics.
Sampling distribution refers to the frequency with which different values of sample statistics occur when different random samples are taken from one population. CLT explains that these sampling distributions ultimately approach normality as more samples are drawn or large enough random samples are taken.
Normal Distribution forms a critical constituent of the Central Limit Theorem because it states that if you have an adequate number of independent observations, then 68% will fall within one standard deviation while 95% will be contained within two strata deviations. This characteristic makes Normal distribution useful for modeling data with unknown parameters since most real-world data tends toward it.
The standard deviation is defined as the square root of variance; they both measure variability. In relation to CLT, these measures help demonstrate how close or dispersed individual observed data sets lie relative to other values produced by resampling processes.
1.Rice J.A., Mathematical Statistics and Data Analysis
2.Bock D.E. Marianne M.H.W., Introduction To Statistical Methods & Data Analysis
3.MIT OCW (http://ocw.mit.edu/courses/mathematics/18-440-probability-and-random-variables-fall-2014/)
4.Doane D.P., Applied Statistics in Business & Economics
5.Kendall M.G. Stuart A, The Advanced Theory of Statistics