DATA SCIENCE Q&A

Collaborative Filtering (CF) is a technique used by recommender systems. Collaborative filtering has two senses, a narrow one, and a more general one. Collaborative filtering is a method of making automatic predictions (filtering) about the interests of a user by collecting preferences or taste information from many users (collaborating). The underlying assumption of the collaborative filtering approach is that if … Read more

Cluster analysis or clustering is the task of grouping a set of objects in such a way that objects in the same group (called a cluster) are more similar (in one sense or another) to each other than to those in other groups (clusters). It is the main task of exploratory data mining, and a common technique for statistical data … Read more

Classification in machine learning and statistics, is the problem of identifying to which of a set of categories (sub-populations) a new observation belongs, on the basis of a training set of data containing observations (or instances) whose category membership is known. Classification is an example of pattern recognition. In the terminology of machine learning, classification is considered an instance of … Read more

Chi-squared test for variances. A chi-square test can be used to test if the variance of a population is equal to a specified value. This test can be either a two-sided test or a one-sided test. The two-sided version tests against the alternative that the true variance is either less than or greater than the specified value. The one-sided version … Read more

Chi-squared test for goodness of fit also written as a χ2 test is any statistical hypothesis test wherein the sampling distribution of the test statistic is a chi-squared distribution when the null hypothesis is true. Without other qualification, ‘chi-squared test’ often is used as short for Pearson’s chi-squared test. Chi-squared tests are often constructed from a sum of squared errors, … Read more

Central Limit Theorem (CLT) is a statistical theory that states that given a sufficiently large sample size from a population with a finite level of variance, the mean of all samples from the same population will be approximately equal to the mean of the population. Furthermore, all of the samples will follow an approximately normal distribution pattern, with all variances … Read more

Causation. Two or more variables considered to be related, in a statistical context, if their values change so that as the value of one variable increases or decreases so does the value of the other variable (although it may be in the opposite direction). Theoretically, the difference between the two types of relationships is easy to identify — an action … Read more

Categorical Variable in statistics is a variable that can take on one of a limited, and usually fixed number of possible values, assigning each unit of observation to a particular group or nominal category on the basis of some qualitative property. In computer science and some branches of mathematics, categorical variables are referred to as enumerations or enumerated types. Commonly, … Read more

CART or Classification And Regression Trees are machine-learning methods for constructing prediction models from data. The models are obtained by recursively partitioning the data space and fitting a simple prediction model within each partition. As a result, the partitioning can be represented graphically as a decision tree. Classification trees are designed for dependent variables that take a finite number of … Read more

Box plots is a quick way of examining one or more sets of data graphically. In statistics, a box plot is a convenient way of depicting groups of numerical data through their quartiles. Box plots may also have lines extending vertically from the boxes (whiskers) indicating variability outside the upper and lower quartiles, which brings up the terms box-and-whisker plot … Read more