# Technical Interview Questions

interview questions shared by candidates

## Technical Interview Questions

Explain/define "Weighted Average". 1 AnswerAn average in which each quantity to be averaged is assigned a weight. These weightings determine the relative importance of each quantity on the average. Weightings are the equivalent of having that many like items with the same value involved in the average. |

50,000 shoppers with a 0.5% conversion rate for a chair that costs $250. Wayfair makes a 27% profit. Next, 50,000 shoppers will get a 10% discount. What is the conversion rate they must achieve to achieve the same profits as before? 13 AnswersStep 1: Calculate profit (250 * 250 * 0.27 = 16875) Step 2: Calculate discount price (250 * 0.9 = 225) Step 3: Calculate price of chair (250 * 0.73 = 182.5) Step 4: Calculate profit margin ( (225 - 182.5)/225 = .19) Step 5: Calculate new conversion rate (225 * 0.19 * x = 16875) x = 395 395/50000 = 0.79% the new conversion rate This is incorrect Old revenue = 50000*250*.005=250*250 New revenue with conversion rate r% = 50000*r*250*.9 = old revenue = 250*250 r = .55% Scenario 1 Number of sales=50,000*.5/100 = 250. Revenue=250*250 = 62,500. Profit is 27%. Therefore 62,500 = 1.27*cost Therefore cost = 49,212.598. Profit = 62,500-49212.598 = 13,287.40. Cost of chair = 250/1.27 = 196.85 Scenario 2 Number of sales = 50,000*r/100 = 500*r (r is new converion rate) Revenue = 500*r*.9*250 Total cost = 500*r*196.85 Profit = 500*r(250*.9-196.85) = 13,287.40 500*r*(28.1496) = 13,287.40. Therefore r = 0.944. The first answer considers profit as margin (percentage of sales) which seems incorrect or needs to be clarified Show More Responses Number 2 is wrong, number 1 is right. Just because revenues equal doesnt mean profits will equal - they sacrifice profits when they decide to give the sale Do they expect you to do this in your head, or will they give you pen/paper and a minute? July 9th Answer is the correct answer. It is not hard: Initial profit is = 50000 * 0.005 * 250 * 0.27 (No need for the calculator yet) After sale profit = 50000 * x * 250 * 0.01 * 0.27 (Still don't need the calc) The question asks for the conversion rate such that profit are the same before and after the sale, so... Initial profit = After Sale profit 50000 * 0.005 * 250 * 0.27 = 50000 * x * (250 - (250 * 0.01)) * 0.27 (divide through & cancel) 0.005 * 250 = x * 225 x = (0.005 * 250) / 225 x = 0.0056 or 0.56% You don't actually need to calculate anything other than the new conversion rate. Why? Look at the equation below: (customer sent = 50000) * (customer bought / customer sent = 0.005 conversion rate) * (revenue / customer bought = 250) * 0.27 (profit / revenue) gives (profit / customer sent). this should be equal to the one after discount. only (revenue / customer bought) changed -> it decreased 10%. therefore, conversion rate needs to increase by (1/0.9), which gives 5.56%. July 9 is correct. Nov 21 is incorrect. July 9 is wrong because the profit margin changes(As sale price changes, but the cost doesn't change) $250 is the actual cost of the chair (profit not included) or the price listed？？ Answer from Nov 21 is correct while July 9 is incorrect. The latter one is just making the revenues equal before and after the sale. It is ignoring the fact that profit % i.e. cost price is also changing after the sale. Before the sale cost price is 182.5*250. After sale cost price would be 182.5*(no >250), as with new conversion rate more customers will be buying. So even if the revenues are equal, profits won't be equal. Total Shoppers 50000 Conversion Rate 0.5 Total Customers 250 Selling Price 250 Profit % 27 Cost price 196.8503937 Profit in $ 53.1496063 Total Sales 12500000 Total Profit 13287.40157 Scenario 2: Selling price 225 Profit 28.1496063 Customers required 472.027972 Conversion Rate in % 0.944055944 Please note that the $250 selling price is (Cost price + 27% profit) on it. So Nov 21, 2014, assumption of doing .27*250 to get the profit is wrong. No of chairs sold = 50000*0.005 = 250 Selling price of chairs sold = 250 Cost price of chairs = 250*(1-0.27) = 182.5 Scenario 1 Total profit = no of chairs sold * selling price - no of chairs sold * cost price = 250*250 - 250*182.5 = 62500 - 45625 = 16875 Total profit = 16875 Scenario 2 No. of chairs sold = x Selling price = 250*(1-0.1) = 225 Cost price = 182.5 Total profit = no of chairs sold * selling price - no of chairs sold * cost price 16875 = x*225 - x*182.5 x = 16875/42.5 x = 397.06 397.06 or 398 chairs should be sold to make the same amount of profit No of chairs sold = 50000*conversion rate 398 = 50000* conversion rate conversion rate = 398/50000 = 0.00796 Required conversion rate would be 0.8% |

I was asked the basic process of O&P sample from start to finish. 1 AnswerProcess sample, build sample, mix samples, centrifuge sample for 5 mins on 1500 rpm, float sample for 10 mins, read sample then release. |

Some of the tasks you'll be required to perform are routine and monotonous. How will you deal with such routine tasks? 2 AnswersMastering routine work allows me to complete tasks effectively in a high throughput manner. Hopefully, this will afford me with free time to learn and master more challenging techniques and better assist the team. Good answer! |

### Senior Technical Writer at Amazon was asked...

How do you plan to ensure that your focus is always on improving the customer experience? 1 AnswerThe first piece of information a good technical writer needs, when presented with a new documentation task, is who the audience will be for this document. It's helpful to get as much detailed data about the audience as possible, preferably before even beginning the task of writing. The better you know your audience, or customers, the better you can serve them. The more you understand them, and their needs, the better you can dazzle them. |

### IT Auditor at SunGard was asked...

What is your experience in operating tools to assess the security of IT networks? 2 AnswersI have spent considerable time working with nmap, but very few other tools. I know many security tools are only available on Linux. I have a strong background using the Linux operating system and feel that I could learn additional tools quickly. I |

How do you represent a real-world quantity in a digital system? 1 AnswerWhat he really wanted me to do was draw the schematic of an ADC input circuit. I don't know why he didn't just ask that in the first place. Since it was a broad question, I spent over 5 minutes explaining binary representation, word size (8/16/32bit), endian-ness, and finally when I mentioned ADCs, he latched onto that and tried to get me to dig deeper. So I drew a block diagram of an ADC, focusing mostly on the interface to the microcontroller, and the channel select multiplexer. He grew increasingly frustrated and tried to get me to draw more detailed sub-circuits for each of the blocks in my diagram. Finally, I got to the actual ADC front end, and I drew a classic textbook R2R ladder circuit, and he seemed satisfied with that. By that point we had spent over 10 minutes in an interview where he was already complaining that he had a lot of ground to cover in limited time. I was so frazzled by the question that I did not even think of mentioning a successive approximation ADC as an alternative to the R2R, even though it's a much more common implementation in my experience. |

Only one tech question that wasn't a brain teaser- technical job related question was about line balance. There's 3 tools in a row with known stabilities. You know the second tool is very unstable but you need to meet demand. 1 AnswerRun more product the previous day in the first machine the previous day. |

What is instrumentation Amplifier (IA) and what are all the advantages? 1 AnswerAn instrumentation amplifier is differential op-amp circuit providing high input impedances with ease of gain adjustment by varying a single resistor |

### QA Analyst at MarkMonitor was asked...

Explain the difference between an inner join and outer join. 1 Answerknow your SQL. |