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Data scientist Interview Questions

"Every business collects data, and it's the job of the data scientist to analyze, interpret, and communicate that information in a way that will help drive company decisions. In an interview, expect to answer technical questions about your ability to perform quantitative tests as well as create clear visualizations of large, complex data sets. Come ready to discuss past projects you've worked on and how you communicate data findings clearly and concisely in order to help solve business-related problems."

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Find the second largest element in a Binary Search Tree

16 Answers

find the right most element. If this is a right node with no children, return its parent. if this is not, return the largest element of its left child.

One addition is the situation where the tree has no right branch (root is largest). In this special case, it does not have a parent. So it's better to keep track of parent and current pointers, if different, the original method by the candidate works well, if the same (which means the root situation), find the largest of its left branch.

if (root == null || (!root.hasRightChild() ) { return null;} else return findSecondGreatest(root, root.getValue()); value findSecondGreatest(Node curr, value oldValue) { if(curr.hasRightChild()) { return (findSecondGreatest( curr.getRightChild(), curr.value)); } else return oldValue; }

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How would you test if survey responses were filled at random by certain individuals, as opposed to truthful selections?

5 Answers

You are compiling a report for user content uploaded every month and notice a spike in uploads in October. In particular, a spike in picture uploads. What might you think is the cause of this, and how would you test it?

3 Answers

How would you build and test a metric to compare two user's ranked lists of movie/tv show preferences?

3 Answers

How do you take millions of users with 100's of transactions each, amongst 10k's of products and group the users together in a meaningful segments?

3 Answers

The three data structure questions are: 1. the difference between linked list and array; 2. the difference between stack and queue; 3. describe hash table.

1 Answer

You're about to get on a plane to Seattle. You want to know if you should bring an umbrella. You call 3 random friends of yours who live there and ask each independently if it's raining. Each of your friends has a 2/3 chance of telling you the truth and a 1/3 chance of messing with you by lying. All 3 friends tell you that "Yes" it is raining. What is the probability that it's actually raining in Seattle?

38 Answers

Write a SQL query to compute a frequency table of a certain attribute involving two joins. What if you want to GROUP or ORDER BY some attribute? What changes would you need to make? How would you account for NULLs?

26 Answers

Given an list A of objects and another list B which is identical to A except that one element is removed, find that removed element.

20 Answers

Consider a game with 2 players, A and B. Player A has 8 stones, player B has 6. Game proceeds as follows. First, A rolls a fair 6-sided die, and the number on the die determines how many stones A takes over from B. Next, B rolls the same die, and the exact same thing happens in reverse. This concludes the round. Whoever has more stones at the end of the round wins and the game is over. If players end up with equal # of stones at the end of the round, it is a tie and another round ensues. What is the probability that B wins in 1, 2, ..., n rounds?

19 Answers
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