Updated Data Analyst Interview Questions and Answers 2021

By Alisha

Last updated on Nov 19 2020

Updated Data Analyst Interview Questions and Answers 2021

Most Commonly Asked Data Analyst Interview Questions 2021

In a data science project, the initial stage involves gathering requirements. Product Owners and Business Analyst input the requirements and transfer these datasets to a Data Analyst. A Business Analyst works intensively on creating the user stories and, a Product Owner gives these user stories a virtual shape with the usage of Scrum and Agile Lifecycle.

The second step involves a Data Analyst to curate peer discussion with the Product Owner. Here, they decide the selection of the dataset and data pool. Here, they collaboratively configure where to look for the data, whether from the third party API or their internal databases.

They figure out what data could solve their problem. Then, a Data Analyst decides the lifecycle of a data science project like feature engineering, feature selection, model creation, Hyperparameter tuning of the model, and lastly, model deployment.

The Lifecycle of Data Science Projects requires a Data Analyst to pose extensive exploratory data analysis to create data reports that are crucial for stakeholders to make further decisions. These reports help in sound decision making based on facts and statistical predictions. Take, for instance, an organization that has launched a new product line of headphones in its business and wants to forecast sales, COGS, returned products, and popularity among the mass consumers. Herewith the help of a Data Analyst, the organization can prepare a report that based on the customer feedback, ratings, and requirements to integrate into its future production.

If you are headstrong enough to choose Data Analyst as your career, then you need to have expertise in Languages like Python and R Programming. You have to learn databases like MySQL, Cassandra, Elasticsearch, MongoDB, to be precise. These databases cater to your structured and unstructured format of data needs. You have to show your expertise in the usage of various Business Intelligence tools like Tableau, Power BI, Qlik View &Dundas BI.

You need to have the following technical skills to ace as a Data Analyst:

  • Basic Mathematics & Statistics
  • Programming Skills
  • Domain Knowledge
  • Data Understanding
  • ELT Tool Knowledge
  • Power Query for Power BI
  • Efficiency in Exploratory data analysis.
  • Identification of both structured and unstructured data.

Putting simply, a Data Analyst has to analyze data creatively then, only the transition from Data Analyst to Data Scientist will be easy. As a Data Analyst, your career prospect can grow as a Market Research Analyst, Actuary, Business Intelligence Developer, Machine Learning Analyst, Web Analyst, and Fraud Analyst so on and so forth. In this article, we discuss in-depth the frequently asked questions for a Data Analyst profile.


Introductory Data Analyst Interview Questions


Explain how are you fit for this role in this particular organization?


You must know that data needs change from companies to companies, and to hit the ground running and give the best answer that demonstrates your worth for this role and organization, you should start with your core competencies.

"I believe I am a highly effective Data Analyst who possesses several core competencies & traits that helps me to produce consistent results for my employer."

I can assess each data analysis task from a strategic perspective. With a high level of numerical and mathematical ability, I have an exploratory& statistical-driven approach to all analysis-tasks. And I also possess strong communication & interpersonal skills, which means I can fit quickly & seamlessly into any team or department. Finally, I have a passion for accuracy & reflect attention to detail in my work. If you hire me for the Data Analyst role, I will carry out High-quality in my job that will help the organization in every possible way.


What are the quintessential skills required to perform this job?

While there are numerous critical skills a Data Analyst must possess to be effective, there are nine that I would deem to be quintessential. These are an investigative & curious approach to all work you carry out. An Ideal Data Analyst must unearth the pattern & meaning behind the numbers in the datasets. He needs to have a strategic approach to understanding and implementing the right analysis techniques to achieve the employer's objectives. He should possess Problem-solving skills with a high degree of a mathematical, methodical, and logical approach to work. He should be strict with deadlines and hold strong interpersonal skills to communicate the interpretation in a non-technical manner.


Core Technical Data Analyst Interview Questions


Differentiate between Data Analysis & Data Mining?

Data Mining is a convergence of disciplines that involves Database Technology, Statistics, Visualization, Information Science, Machine Learning. We create probability distributions devising Descriptive Statistical methods & Inferential Statistics to get an estimation, Hypothesis testing, model scoring, Markov Chain & generalized model classes. It has a vast structured database from where the data scientists and Data Analyst defines the data patterns and trends.

While Data Analysis involves the examination of the datasets to draw inference out of it, with the test hypothesis, we make data-driven decisions. Data Analytics usage involves Artificial& Business Intelligence models comparing from the small, medium, and large databases with SQL and NoSQL data. The output direction is to have actionable insights, verify or reject the hypothesis.


Illustrate Data Validation?

When there is a conflict in responses, we use Data Validation methods to identify inaccuracies. We can use the Holdout Strategy & K-Fold strategy to get Data Validation in Machine Learning. It is also known as input validation that ensures uncompromised data transmission to programs to avoid code injection. The types of Data Validation includes:

  • Constraint validation
  • structured validation
  • data range validation
  • code validation and
  • datatype validation.

These data validation routines, rules test the correctness and security of the incoming data.


How can you ascertain a sound functional data model?

To assess the soundness of a data model, we should start with correctness in predictability. A good data model does not fluctuate or disrupts with minor or significant alterations in the data pipeline. And the data model should be adaptable to scalability refraining from dysfunctionalities. The model must be presentable and comprehensible to a Data Analyst& its stakeholders.


How an Analyst strategize on account of missing data?

The process of detecting the suspected or missing data starts with the application of methods like Model-based or deletion methods. Then, the analyst creates a validation report out of it and includes every detail about the missing data in the Report. Validation reports direct whether or not the incoming data is compromised or unsafe to transmit into the program. Further, the Data Analyst scrutinizes the process to avoid code injection. He makes sure that the data induced now is ready to replace the invalid data or inculcate with proper validation code.


What is Outlier?

Statistics define it as a data point that possesses significant variation for the rest of the observation. For a Data Analyst, the presence of an Outlier indicates measurement error. These errors are divergent from the rest of the sample. We can divide it into the following types:

Point Anomalies:Point Anomalies or Global outliers are extensively divergent and fall outside the dataset.

Conditional-Outlier: Mostly found in time series data, this data point deviates from its sample and remains in the dataset as seasonal patterns.

Collective-Outlier: You detect collective outliers when the individual data points form a subset of the whole dataset and then get deviated.


Is retraining a model dependent on the data?

Now the competitive world, business runs 24*7*365. We cannot make the mistake of having a redundant system. We need our system built in a way that is adaptable to every major or minor alteration within a fraction of milliseconds. The model has to be fast-paced to retain the burden of the business.

Businesses invoke changes and many times are the reason for a trend or change. Hence, retraining the model is recommended to closely work with the changing paradigm of the business and adapt to uncertainties and forecasted course.


Illustrate some problems occurring while analyzing data?

Many problems occur when you perform the analysis. If the source of data is POOR, then cleaning the data will involve ample time. The data can also be indifferent format so, we will face representation problems when we combine the data & this will result in excessive delay. And if the data is missing or incomplete, then analysis becomes quite problematic. Data Analysts also face problems such as spelling mistakes, duplication, and suspected data while, analysis.


Ellucidate A/B testing?

A/B Testing directs end-users to ads, welcome emails, and web pages. It segments the results based on control & variance. This hypothesis works best for website optimization by gathering website performance data & reveal different versions of the webpage to the visitor.


How will you differentiate Bias from Variance?

We can define data bias as a type of error that has a heavily weighted dataset. There are many forms of BIAS like; missing data, corrupted data, data selection, data conformation, and algorithmic interpretation. Its types include sample bias, exclusion, measurement, recall& racial, observer, and association biases. Troubleshooting data bias in machine learning projects starts with determining its presence that helps to take necessary action for remedy.

Variance or Over-fitting is the type of error that occurs due to the fluctuations in the dataset.

While the relationship between Bias and Variance in most of the cases is to minimize at least one of the two errors here, Regularization helps to limit VARIANCE and reduce its optimal capacity.


Differentiate between data profiling and Data mining?

Data mining helps to identify patterns by correlating with the large datasets, the purpose of data mining defines the data patterns and trends. It has a vast structured database from where the data scientists analyze the data. Data Analysis involves the examination of the datasets to draw inference out of it with the test hypothesis we make data-driven decisions.

Data profiling is exploratory activities of analyzing data from an internal or existing dataset to determine structure, content, quality. They can be raw or informative summaries that help to recognize and use the metadata. The analyst mainly tries to create a knowledge base of qualitative and accurate information on the datasets.


State some of the significant Hypothesis testing?

Before we test, we create our hypothesis and identify the test statistic & probability by specifying the significance level. Then we state the decision rule and collect the data from the distribution to make statistical or data-driven decisions.


Hypothesis testing in R Language.

There are two types of error occurrences in Hypothesis testing in the R language. The type I error is an alternative hypothesis with a designated standard deviation. The type II error is a Null Hypothesis with designated SD. The threshold value serves as metrics in Hypothesis testing in R Language. When the value of Type-I error is less then we reject the alternative hypothesis. And if the value goes beyond the threshold value then we accept the alternative hypothesis.


It is used to compare two samples to determine their origin & variance. A big T-value reveals that the sample is from different groups. But a small T-value represents samples belong to similar groups. The purpose of the independent t-test is to identify the difference between two means.

T= variance between groups/ variance within groups.


Analysis of Variance tests, one independent variable with two or more means. It works on testing the difference between the means of the two groups on a single variable.


Data Analyst Interview Questions based on SAS & SQL


SAS or Statistical Analysis System is a command-driven independent statistical software suite by SAS institute. It is used for Artificial Business Intelligence, fraud investigation & predictive analysis. SAS extracts data and categorizes it to identify and analyze patterns in it. It has an edge over BI tools by programmatically transforming the raw data and using a drag & drop interface to analyze the data.

The SAS suite can reduce the burden of companies by doing analysis with the help of a single Data Analyst. It can even make predictions of an outcome with missing data. This software suite also reduces the work of a Data Analyst by performing multiple tasks at a click. Though it has its alternatives like Python, R Language, Excel, Hive, Apache Spark & Pig, but the GUI it provides is commendable for the commercial analytics market.


Define Interleaving the SAS?

Interleaving in SAS is a method to vertically combine SAS datasets. When we append or concatenate data sets, the observations from each individual dataset remain grouped together in the same order in the combined data set. If you want observations in the combined data set to mix together based on the values of one or more common variables then you can do this with a process known as interleaving the data set.


What are the SAS programming practices for processing large datasets? How to do a "Table LookUp" in SAS?

Some of the best SAS programming practices are as follows:

  1. Sampling Method using Subsetting.
  2. Commenting on the lines 
  3. Using Data Null

There are many ways to do a "Table Lookup" in SAS and they are as follows:

  • Arrays
  • Format Tables
  • Direct Access
  • Match merging


How to control the number of observations?

We can control the number of observations or variables with the help of the FIRSTOBS & OBS option.


How SAS is self-documenting?

SAS creates & stores information about the data set during the compilation. 



These are the frequently asked interview questions, & by going through the same you will be able to grasp and cover most of the important topics. Once and for all!

To explore certification programs in the Data Science field, chat with our experts, and find the certification that fits your career requirements. 


Suggested Reads:


Data Analyst Guide - Benefits, Tools and Career Scope



Explore popular Data Science courses:


Data Analyst Course

Big Data Hadoop and Spark Developer Course

About the Author

Sprintzeal   Alisha

Technology Content Writer with Experience in Creating Content for Data Science and Other Popular Domains.

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