Top 5 Data Scientist Interview Questions and Answers

Let’s talk about the “Sexiest Job of the 21st Century”. Yes, you heard it right, according to a survey of Harvard, the data scientist role is placed at #1 out of 25 best jobs on the American list. By 2020, demand for this role has raised to 28 percent, and it should be of no surprise that in the coming era of big data and machine learning, data scientists will be the new rockstars. To step into the world of big data, a candidate must pass the data science interview. Due to the importance of data, data science has gained utmost importance and is considered the new oil of the IT industry which when processed properly gives outstanding results to customers and stakeholders.

Data scientists can solve real-time problems using new and trendy technologies. E.g.- They can help the delivery guys by showing the fastest possible path to reach their respective destination, can recommend products to the user based on their search history, and can detect frauds in credit-based financial applications.

1. What do you understand when the p-values are high and low?

A p-value determines the results equal to or more than the results achieved under a specific hypothesis when the imaginary null hypothesis is correct. It is the measure of the probability and indicates the probability that the observed difference occurred by chance.

• Low p-value i.e., values <0.05 represents that the null hypothesis can be ignored, and data is not likely with true null.
• High p-value i.e., values >0.05 means the null hypothesis can’t be ignored and data is like with true null.
• P-value=0.05 indicates null hypothesis can go either way.

2. What is sampling and which techniques are used for sampling?

This is one of the most commonly asked data scientist questions which if answered correctly can increase your chances of getting hired. It is impossible to do data analysis on a large volume of data at a given time, especially on larger datasets. It is mandatory to take some data samples that can represent the whole data and then perform an analysis on it. While doing this, the sample data we are taking must be taken in a way that truly covers the whole dataset. This process is known as Sampling.

Categories of techniques used for sampling

• Probability Sampling Techniques: Simple Random Sampling, Stratified Sampling, Clustered Sampling.
• Non-Probability Sampling Techniques: Convenience Sampling, Snowball, and Quota Sampling.

3. What is selection bias and its types?

When researchers have to make a decision regarding which participant to study, selection bias occurs in that case. It is associated with the research where participant selection is not random and is also known as selection effort.

Types of Selection Bias.

• Sampling Bias: Some members of a dataset have fewer chances of getting selected than others, which results in a biased sample and hence causes an error known as sampling bias.
• Time Interval: If we reach any extreme value, we can stop the trials early. But if all variables are similar, the variable with the high variance has more chance of achieving the extreme value.
• Data: When specific data is picked randomly, and the agreed criteria are not followed.
• Attrition: Loss of the participants is known as attrition.

4. What do you understand by logistic regression? Explain it with an example.

Logistic regression which is also known as the logit model is a technique that predicts binary outcomes from the linear combinations of predictor variables.

Example: Let’s suppose we want to predict the results of elections for a political leader. We will assume whether he is going to win or not. Therefore, the outcome is binary i.e. win (1) or loss (0). But the input will be a combination of various linear variables like money spent on advertisement, their past work history, etc.

5. Data cleaning is very crucial. Why? What are the advantages of cleaning it?

As dirty data often results in poor and incorrect output which can have damaging effects, it is very important to do data cleaning to have correct and relevant information.

• Cleaned data highly increases the accuracy of a model and gives good predictions.
• It results in increased speed and efficiency of an application.
• Data cleaning helps a user to identify any high-risk issues and helps them to fix them.
• It maintains data consistency and helps in removing duplicates.
• Data cleaning can also increase the data quality.

Originally published at https://www.bestinterviewquestion.com.