SQL and Statistics Interview Questions | Day 7

SQL and Statistics Interview Questions – Day 7 has solved questions from basic statistics, SQL, and a case study. If there is some mistake in the answers, then do comment below. Try to add more points in the case study section.
SQL and Statistics Interview Questions

Welcome to the 6th Day of Machine Learning Interview Questions.
You can go through the question and answer for
Day 1
Day 2
Day 3
Day 4
Day 5
Day 6

Machine Learning Interview Questions

In this series, all you need to do is to go through the questions and try to attempt it with whatever knowledge you have.

Before or after you attempt the questions, do go through the complete road map about what you need to study to crack an analytics role. We have covered from 3rd year college student to 8 years of analytics or non-analytic experience. Make sure you understand where to emphasize more(after all by the end of the day you want to crack an interview)

Complete Roadmap for cracking an Analytics Role in the next 30 days

Now, coming back to our questions. Remember, these are the most asked questions in any interview, if you are shy to answer the questions in the comment section, then do make sure to Google the answer and jot it down in your notebook.

1. What percentage of value lies between the Mean and one Standard deviation(both positive and negative)
~68%

2. Give the relation of Mean, median, and mode in a positively skewed distribution
Mean > Median > Mode

3. Negatively skewed distribution?
Mode > Median > Mean

4. What is the sum of squared deviation?
The Sum of Squared deviation is a measure of the total variability of a set of scores around a specific number

5. Why do we need to square the terms?
We need to square the terms so that the values above the mean do not cancel those below the mean.

6. How to find the Third highest salary in the Employee table using self-join?
Select * from Employee a Where 3 = (Select Count (distinct Salary) from Employee where a.salary<=b.salary

7. What is the difference between the primary key and the candidate key?
To identify each row of a table, a primary key is used. For a table, there exists only one primary key.
A candidate key is a column or a set of columns that can be used to uniquely identify any record in the database without having to reference any other data.

8. What are the measures of spread?
The measures of spread are
a. Variance
b. Standard Deviation
c. Covariance
d. Sample Correlation

9. What is the use of NVL function in Oracle?
NVL function is the most important function to replace a null value with another value.
Example:
select NVL(null,’ Amit’) from dual;
which will give you output as Amit.

10. Case Study
If you have to recommend a product to a customer who has already filled his cart, then what data will you look for? Basically, how will you recommend a product to an e-commerce customer?
There could be multiple things that we can look for
a. If the customer has brought the product A, then we should look in the data to find out the product that compliments that product. We can do this by looking into the purchase history of other customers who have brought the product A
b. We can get the cart information of the customer and look for those items which he has removed from the cart. At the check-out, you can again ask him if he wants to buy it
c. We can also look for a better product option for the customer. Suppose the customer is willing to pay $3 for soap, then we can show then ads or recommendations of a $5 soap with a better review
d. We can also look for the previous cart history of the customer to see if he is missing something which he used to buy regularly

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