This collection focuses on the understanding of discrete and continuous random variables. It also throws light on concepts like expected value, variance, covariance and correlation of the random variables. The major part of this collection focuses on what is sampling and why we require estimators. Once we choose estimators, how do we know which is a good estimator and what are the measures for testing it. It also throws light on Hypothesis testing- 5% significance level and 1% significance level test and the difference between the two. You guys will get a clearer understanding by working out some exercises on the concepts of Probability distribution, expected value, variance, Unbiasedness and Efficiency.