# Ace your next data science interview

Get better at data science interviews by solving a few questions per week. Join thousands of other data scientists and analysts practicing for interviews!

## How it works?

### We write questions

Get data science interview questions frequently asked at top companies.

### You solve them

Solve the problem before receiving the solution the next morning.

### We send you the solutionPremium

Check your work and get better at interviewing!

## The Schedule

We send data science interview questions 3x per week

### Monday

Interview question #1

### Tuesday

Get answer to interview question #1

### Wednesday

Interview question #2

### Thursday

Get answer to interview question #2

### Friday

Interview question #3

### Saturday

Get answer to interview question #3

## Sample Questions

### Question

Suppose there are 15 different color crayons in a box. Each time one obtains a crayon, it is equally likely to be any of the 15 types. Compute the expected # of different colors that are obtained in a set of 5 crayons. (Hint: use indicator variables and linearity of expectation)

### Solution

```We enumerate the crayons from 1 to 15. Let Xi indicate when the ith crayon
is among the 5 crayons selected.

So,
E(Xi) = Pr {Probability that at least one type i crayon is in set of 5}
E(Xi) = 1 – Pr {no type i crayons in set of 5}
E(Xi) = 1 – (145 /15)

Therefore, the expected # of crayons is:

= ∑15 E(Xi)
= 15[1-(145/15))]
= 4.38
```

## See what others are saying

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Deepti
Data scientist, Redhat

InterviewQs helped me cover all the basics of technical data science interviews, from SQL/Python to probability/statistics. The confidence/knowledge I gained from the service was incredibly useful, helping me land a data scientist position at Red Hat.

Dilan