September 8, 2010
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J company Interview...
: O... You know MySQL? How much do you know about it?
: just some simple insert / delete / update statements...What the fuck? Do I know just so less in MySQL? Anymore can I say about? Well... May be... that's all...
: So... Do you know what is arbitrage?
I think he asked me this question not because I am majoring in Finance... It is a common question to all candidate. He asked me about MySQL when he read up to the point MySQL, and ask me this question after finish reading the whole CV.
: um.... yes... that means I can obtain positive profit at the end no matter what ...
(something like that la, I do not know jargons in Finance)then the the main course of the interview started, without any question like "Briefly introduce yourself first.", "What are your strong points?", "What are your weak points?"
: So... Let's start with some mental math.
(Note: No pencil and paper are provided, and please answer immediately)
Question 1 : 17+24
Question 2 : 97-126
Question 3 : 13x21
Question 4a: you enter a game, I will pay you the result of rolling a die. i.e. the result of rolling the die is 1, then I will pay you $1. And of course I won't let you enter the game freely. How much are you willing to pay to enter the game?I am glad that I can answer question 4a correctly without any hesitation. But I know that, from the point of view of the interviewer, this question means nothing. I know that...
Question 4b: now I give you two dice, you can choose to roll again with the second die, but then you lose the chance of getting the paid determined by the first die. i.e. first die is 4 but the second die is 3, because you give up the chance of taking prize in first round, you can only take $3. What is your strategy? Why?
sigh... totally skin collected... Got serious flu yesterday, and getting better this day but still feeling a little dizzy... Attended an interview under this situation... sigh... Though I know it made no difference to the interview... I do not think that I can answer this question when I am healthy =.=....
Before entering the interview, a CEDARS staff gave me the summary sheets written by the previous candidate, I only knew that it would be purely mathematic and statistic 15 minutes before I entered the interview room... (or I should not say so, because the hints found in the Internet also mentioned that...)
Actually Question 4 can be found in the Internet, last night I thought about it very briefly, the solutions I generated was what I answered this afternoon. (urgh? You trust yourself even if you are dizziyng?)
My answer is: If the first result is smaller than or equal to 3 then I will roll the second dice.
: Why?
: (um......) because the expected value on the second die is also 3.5, I should roll one more time if the result is less then this value.
: Nope.
: (um...... start to make a random guess) ...if the first time I get 6 then .... if the first time I get 5 then .... if the first time I get 4 then....<< Obviously it is a nonsense answer.
And then my interview stopped here, coz I was sucked even in the most basic statistics question, there was no meaning to continue the interview. Then he spent a long period on explaining the solution to me...
A common last question: Do you have any question on J Company?
: (prepared long long time ago) Why is OCaml not popular in the industry...?
The answer is not important anyway...
Actually Question 4 has part c... : What if I offer you 3 dice now? What is your strategy?
Sigh, I should have found someone to discuss the question with me... sigh... After the interview I met Barry, and asked him this question...
B: O! Bryan has asked me the same question before! And the answer is...
The answer is : Roll the second die if the first die is 1/2/3... Probably you get the same right? What really matters is the explanation.
Following the above strategy, what is the total expected value? ... the calculation can be divided into two parts here : the first die and the second die. coz we are going to take the money if the first result is 4/5/6, the expected value of the money we get from the first die is therefore 5. And for the second die, the expected value is 3.5. Then we have to figure out, in what probability will we choose the roll the second die? Answer is 1/2, 1/2/3 vs 4/5/6, 50-50 right? so the expected value of this strategy is 5/2 + 3.5/2 = 4.25.
By the same method, you can calculate the expected value of any strategy. There are at most only 6 strategies... And actually the interviewer was satisfied with the number 4.25...
So... and the case is same as 3 dice... try to calculate it by yourself la
And, more frustrating... is that, I met another interviewee after the interview, he met another interviewer... and he said that... the other interviewer did not ask him for explanation ...
WHAT THE FUCK?
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