General Data Science and SQL Online Test
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Sign Up To Use This TestThe General Data Science and SQL test assesses a candidate’s ability to analyze data, extract information, suggest conclusions, and support decision-making. It also tests a candidate’s knowledge of SQL queries and relational database concepts.
It's the ideal test for pre-employment screening. Data scientists and data analysts need to be able to extract knowledge and insights from data. Often, they also need a solid understanding of SQL to interface and access an SQL database efficiently.
This test requires candidates to demonstrate their ability to apply probability and statistics when solving data science problems and write SQL queries that extract and combine data.
Recommended Job Roles
Data Analyst
Data Scientist
Sample Candidate Report
Sample Free Questions
Students
3min
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Easy
Easy
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CODE
SQL
Aggregation
Select
Public
SQL
SQL is the dominant technology for accessing application data. It is increasingly becoming a performance bottleneck when it comes to scalability. Given its dominance, SQL is a crucial skill for all engineers.
Aggregation
An aggregate function is typically used in database queries to group together multiple rows to form a single value of meaningful data. A good programmer should be skilled at using data aggregation functions when interacting with databases.
Select
The SELECT statement is used to select data from a database. It is the most used SQL command.
Public
Public questions (free account) are common interview questions. They are great for practicing, or if you want to filter candidates using the classic problems.
Given the following data definition, write a query that returns the number of students whose first name is John. String comparisons should be case sensitive.
TABLE students id INTEGER PRIMARY KEY, firstName VARCHAR(30) NOT NULL, lastName VARCHAR(30) NOT NULL
Enrollment
5min
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Easy
Easy
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CODE
SQL
Conditions
Update
Public
SQL
SQL is the dominant technology for accessing application data. It is increasingly becoming a performance bottleneck when it comes to scalability. Given its dominance, SQL is a crucial skill for all engineers.
Conditions
Conditional statements are a feature of most programming and query languages. They allow the programmer to control what computations are carried out based on a Boolean condition.
Update
The UPDATE statement is used to modify the existing records in a table and is one of the most used operations for working with the database.
Public
Public questions (free account) are common interview questions. They are great for practicing, or if you want to filter candidates using the classic problems.
A table containing the students enrolled in a yearly course has incorrect data in records with ids between 20 and 100 (inclusive).
TABLE enrollments id INTEGER NOT NULL PRIMARY KEY year INTEGER NOT NULL studentId INTEGER NOT NULL
Write a query that updates the field 'year' of every faulty record to 2015.
Pet Detection
5min
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Easy
Easy
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NUM
General Data Science
Confusion matrix
Machine learning
Public
General Data Science
When we need to discover the information hidden in vast amounts of data, or make smarter decisions to deliver even better products, data scientists hold the key to the answers you need.
Confusion matrix
A confusion matrix is a specific table layout that allows for visualization of the performance of an algorithm. Each row of the matrix represents the instances in a predicted class while each column represents the instances in an actual class (or vice versa). As one of the most common techniques for analyzing classifier performance, it’s important for all machine learning developers.
Machine learning
Machine learning is the scientific study of algorithms and statistical models that computer systems use to perform a specific task without using explicit instructions, relying on patterns and inference instead. It’s important for all tasks where it’s infeasible to construct conventional algorithms, which is often the case in Data Science.
Public
Public questions (free account) are common interview questions. They are great for practicing, or if you want to filter candidates using the classic problems.
A classifier that predicts if an image contains only a cat, a dog, or a llama produced the following confusion matrix:
| True values | ||||
| Dog | Cat | Llama | ||
| Predicted values | Dog | 14 | 2 | 1 |
| Cat | 2 | 12 | 3 | |
| Llama | 5 | 2 | 19 | |
What is the accuracy of the model, in percentages?
Premium Questions
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Questions
Authors, Cheapest Product, Countries, Developers, Employee Manager, Merge Stock Index, Movies, Movies Live, Rectangles, Retirees, Sales, Student Activities, Tasks, Transactions, Youngest Child, Manager Sales, Average Salary, Movie Genres, Auto Show, Poll, Subscribers, Age and Earnings, Rain, Patient Classification, CTR, Wine Quality, Credit Wizard, Student Rankings, Welfare Organization, Bacterial Growth, Student Max ScoreSkills
SQLSQL
SQL is the dominant technology for accessing application data. It is increasingly becoming a performance bottleneck when it comes to scalability. Given its dominance, SQL is a crucial skill for all engineers.
Conditions
Conditional statements are a feature of most programming and query languages. They allow the programmer to control what computations are carried out based on a Boolean condition.
Select
The SELECT statement is used to select data from a database. It is the most used SQL command.
Aggregation
An aggregate function is typically used in database queries to group together multiple rows to form a single value of meaningful data. A good programmer should be skilled at using data aggregation functions when interacting with databases.
Subqueries
Subqueries are commonly used in database interactions, making it important for a programmer to be skilled at writing them.
Ordering
Knowing how to order data is a common task for every programmer.
Bug fixing
Everyone makes mistakes. A good programmer should be able to find and fix a bug in their or someone else's code.
Left join
LEFT JOIN is one of the ways to merge rows from two tables. We use it when we also want to show rows that exist in one table, but don't exist in the other table.
Union
The UNION operator is used to combine the result-set of two or more SELECT statements. It is often used when a report needs to be made based on multiple tables.
Group by
The GROUP BY statement groups rows by some attribute into summary rows. It is a common command when making various reports.
Insert
Even though most database insert queries are simple, a good programmer should know how to handle more complicated situations like batch inserts.
Joins
A normalized database is normally made up of multiple tables. Joins are, therefore, required to query across multiple tables.
CTE
A CTE (Common Table Expression) is a temporary result set that can be referenced within another SELECT, INSERT, UPDATE, or DELETE statement. Recursive CTEs can reference themselves, which enables developers to work with hierarchical data.
SQL CASE
The CASE statement is SQL's control statement. It goes through conditions and returns a value.
General Data Science
When we need to discover the information hidden in vast amounts of data, or make smarter decisions to deliver even better products, data scientists hold the key to the answers you need.
Poisson distribution
Poisson distribution is a discrete probability distribution that expresses the probability of a given number of events occurring within a fixed interval of time and/or space, if these events occur with a known average rate and independently of the time since the last event. As one of the most widely used distributions, it is important for all Data Scientists to be familiar with it.
Probability
Probability theory is the foundation of most statistical and machine-learning algorithms.
Linear regression
Linear regression is one of the most frequently used methods for data analysis due to its simplicity and applicability to a wide variety of problems.
Classification
Classification is the problem of identifying to which set of categories a new observation belongs, on the basis of a training set of data containing observations whose category membership is known. As one of the common tasks in machine learning, it’s important for all data scientists.
ROC
A receiver operating characteristic curve is a graphical plot that illustrates the diagnostic ability of a binary classifier system as its discrimination threshold is varied. The curve is created by plotting the true positive rate against the false positive rate at all possible decision boundaries. It is useful for selecting possibly optimal models and to discard suboptimal ones prior to specifying decision boundaries.
Decision boundary
In a binary classification problem with two classes, a decision boundary or decision surface is a hypersurface that partitions the underlying vector space into two sets, one for each class. The classifier will classify all the points on one side of the decision boundary as belonging to one class and all those on the other side as belonging to the other class.
Binomial distribution
Binomial distribution is the discrete probability distribution of the number of successes in a sequence of independent yes/no experiments, each of which yields success with a given probability.
p-value
An important concept, p-value is defined as the probability of obtaining a result equal to or "more extreme" than what was actually observed, when the null hypothesis is true.
Correlation
Correlation is any statistical relationship, whether causal or not, between two random variables or two sets of data. As one of the fundamentals of Data Science, correlation is an important concept for all Data Scientists to be familiar with.
Multicollinearity
Multicollinearity is a phenomenon in which one predictor variable in a multiple regression model can be linearly predicted from the others with a substantial degree of accuracy. In this situation the coefficient estimates of the multiple regression may change erratically in response to small changes in the model or the data. As such, it’s important for all data scientists to check for collinear variables when looking at individual predictor variables in multiple regression models.
Decision tree
A decision tree is a decision support tool that uses a tree-like model of decisions and their possible consequences. It is usually a tool for displaying an algorithm that contains only conditional control statements and is a must-know for every data scientist.
Curve Fitting
Curve fitting is the process of constructing a curve, or mathematical function, that has the best fit to a series of data points. This is basic knowledge of every data scientist.
Performance tuning
The performance of an application or system is important. The responsiveness and scalability of an application are all related to how performant an application is. Each algorithm and query can have a large positive or negative effect on the whole system.
Score Distribution
# of candidates
| 0-33% | |
|---|---|
| 34-66% | |
| 67-100% |
Score