Nibcode Solutions Blog

Although the most popular way to assess whether a candidate is right for a job position is the one-to-one interview, psychometric tests are used by many employers as a filtering mechanism at an early stage of the recruitment process, especially for technical jobs. They are the most common tools used by recruiters to assess intelligence, skills and personality.

As with any kind of test, you can improve your performance if, beforehand, you know what to expect and you have enough practice. Psychometric Training is, unarguably, one of those tools that will help you to improve you reasoning skills, and overcome most of the logical and abstract reasoning tests applied by recruiters. It not only provides hundreds of free problems to practice, but also useful explanation to help you to understand the logic behind every problem.

One of the most used matrix decompositions is the eigendecomposition, which is related to the concept of diagonalization, and decomposes a matrix into eigenvectors and eigenvalues. Eigendecomposition plays a key role in computer vision and machine learning in general. Well known examples are PCA (Principal Component Analysis) for dimensionality reduction or EigenFaces for face recognition. As another important example of the use of this decomposition, Google, relies upon eigenvalues and eigenvectors to rank pages with respect to relevance.

Although this problem of the week doesn't request to find the eigendecomposition of a matrix, it is related to the concept of eigenvalues, and to solve it, you will need to know the foundation of the procedures used to compute them.

Orthogonal bases have some practical advantages and are very useful when dealing with projections onto subspaces. These bases are defined in spaces equipped with an inner product also called a dot product, and by definition, a basis is called orthogonal if every pair of basis vectors are orthogonal, that is, their inner product is 0. When the length of each vector is 1 (vectors are normalized), the basis is called an orthonormal basis.

In an inner product space, it is always possible to get an orthonormal basis starting from any basis, by using the Gram-Schmidt algorithm. To solve this problem of the week you will need to prove you master the Gram–Schmidt process, and you also need to compute the change of basis matrix.

In Linear Algebra the most important subspaces are tied to matrices. One of these subspaces is the Column Space, which consists of all linear combinations of the columns of a matrix. This subspace, spanned by the columns of a matrix, is crucial in Linear Algebra and it is related to 4 of the most important subjects: Matrices, System of Linear Equations, Vector Spaces and Linear Transformations.

This problem of the week is about this subspace, but you should also apply the concept of symmetric matrix.

Linear transformations are one of the key concepts of Linear Algebra, and they are considered the most useful part of this branch of mathematics. A linear transformation is a mapping between two vector spaces that preserves linearity.

There are some important concepts students must master to solve linear transformation problems, like kernel, image, nullity, and rank of a linear transformation. This problem of the week will deal with the kernel (the set of vectors in the starting vector space which are transformed to the zero vector) and nullity of a linear transformation, and its solution only requires to know how to work with matrices and make elementary row operations.