### 45 data analyst interview questions

Interviewing for a role as a analyst? You've come to the right place! Below we've curated a list of data analyst interview questions from multiple sources to help make your preparation easier.

For a data analyst interview, the interviewer will ask a wide range of topics covering statistics, programming (Python and/or SQL), data modeling, and overall business acumen. This guide contains 45 data analyst interview questions, broken out by high-level topics.

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### Statistics

Statistics are the guiding principles to collection, organizing, and interpreting data. A general familiarity with stats will be necessary for any data analyst. You don't necessarily have to be an expert in statistics, but use the job description to gauge the level of familiarity necessary.

1. What is r^2? What are some other metrics that could be better than r^2 and why?
2. What is sampling? Can you provide an example of a sampling method? Can you provide an example of a time in the past where you needed to use sampling?
3. What is Type I error and how is it different from Type II error?
4. How would you explain a linear regression to a non-technical person?
5. What are the assumptions of linear regression?
6. What is selection bias?
7. How would you explain a logistic regression to a non-technical person?
8. Be prepared to answer conditional probability questions and Bayesian probability questions.
9. What are the assumptions of a logistic regression?
10. What is a p-value?
11. What is a confidence interval and how do you interpret it?
12. How would you estimate the disease probability in a city, given the probability is very low nationwide?
13. In any 15-minute interval, there is a 20% probability that you will see at least one shooting star. What is the probability that you see at least one shooting star in the period of an hour?
14. You have an 50-50 mixture of two normal distributions with the same standard deviation. How far apart do the means need to be in order for this distribution to be bimodal?
15. A couple tells you that they have two children, at least one of which is a girl. What is the probability that they have two girls?
16. What is the probability of rolling a 4 or 7 for two 6 sided dice?
17. On a dating site, users can select 1 out of 10 adjectives to describe themselves. A match is declared between two users if they match on at least 4 adjectives. Given a pool of 10 independent users, what is the probabilty that at least two will be a match?
18. You have two coins, one of which is fair and comes up heads with a probability 1/2, and the other which is biased and comes up heads with probability 3/4. You randomly pick coin and flip it twice, and get heads both times. What is the probability that you picked the fair coin?

### Programming

Another large portion of data analytics is aggregating and processing data. As a data analyst, having a familiarity with programming can provide you an advantage in the interview process. It's common for data analysts to be fluent in SQL/Excel, but often Python is not an explicit requirement. By knowing at least a little bit of programming you can stand out both in the interview process and on the job (e.g. using programming to automate work/analysis will go a long way). Below are some practice data science interview questions covering Python and general programming.

1. How would you clean a data set in Python (or any other language)?
2. How would you drop null values in a Pandas dataframe?
3. Given a list of tweets, determine the top 10 most used hashtags. You can assume the list is provided in a Python dataframe.
4. Write an algorithm that can calculate the square root of a number, using Python.
5. Explain some examples of automating data analysis/related processes using programming.
6. How would you replace all NaN values in a Pandas dataframe?
7. {Whiteboard} Create a simple Python function to take in an integer value, multiply it by 2, and append it to an array.
8. {Whiteboard} Create a simple Python function to determine if a given Python string contains a baseline string, 'as'. If the given string does contain 'as', print 'yes' otherwise print 'no'.

### SQL

As a data analyst, being able to pull information directly from datatables will be very important to a lot of employers. SQL is the most common language for the job, and is becoming a standard requirement for many data analyst roles. If you can master basic/intermediate SQL this portion of the interview will be a breeze.

1. What does the GROUP BY function in SQL do?
2. What is the difference between an inner join and a union?
3. How do you eliminate duplicate rows from a query result?
4. Given a impressions table with ad_id, click (a boolean indicator that the ad was clicked), and date, can you write a SQL query that will tell me the monthly click-through-rate all ads?
5. Can you write a query that returns the name of each department and a count of the number of employees in each? Below are the tables' schema:
• EMPLOYEES containing: Emp_ID (Primary key) and Emp_Name
• EMPLOYEE_DEPT containing: Emp_ID (Foreign key) and Dept_ID (Foreign key)
• DEPTS containing: Dept_ID (Primary key) and Dept_Name
6. Explain to me a common use case of windowing functions.
7. What's the difference between a right join and a left join?
8. What is a subquery?

You can be a great data analyst, but if you're unable to communicate the results of your analysis, or you don't mesh well culturally that could cost you the job. Because of this, it's important to have a few situations prepared prior to interviewing that highlight your communication skills, character, and capabilities! Keep it cool, and let your personality shine through!

1. Tell me about a time where you had to present a detailed analysis to a high-level executive.
2. Introduce me to something you’re passionate about.
3. Tell me about a time you failed, and what you have learned from it.
4. Tell me about a time you had to influence someone without authority.
5. What have you done in your previous job that you are really proud of?
6. What’s a project you would want to work on at our company?
7. Tell me about a time where you resolved a conflict.
8. Tell me about a time when you took initiative.
9. Suppose you encounter a tedious, boring task. How would you deal with it and motivate yourself to complete it?
10. What are your top 5 predictions for the next 20 years?
11. What personality traits do you conflict with?

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