ABSTRACT
Data collection is a crucially important step in Statistics. Sampling errors are caused by the mere fact that only a sample, a portion of a population, is observed. For most of reasonable statistical procedures, sampling errors decrease as the sample size increases. Comparing two brands of notebooks, a senior manager asks all employees of her group to state which notebook they like and generalizes the obtained responses to conclude which notebook is better. Simple descriptive statistics measuring the location, spread, variability, and other characteristics can be computed immediately. Statistics showed where the average value and certain percentages of a population are located. Now the variability of our variable is measured, and how unstable the variable can be, and how much the actual value can differ from its expectation. A histogram shows the shape of a pmf or a pdf of data, checks for homogeneity, and suggests possible outliers.
