Teaser Tuesday! July 1, 2014

Summer is in full swing! Time to get those brains as warmed up as the rest of you.

Note: If you could all please input your answers using the previously noted html code it will allow others to answer without having a spoiler. Also, in your answer, do not include any ' or " or it will not work properly. Also, if you are having trouble getting the code to work, please do not be the first person to answer.

Question

I am thinking of a number between 1 and 100. You can guess a number and I will tell you if it is high or low. If you get it right on the first guess I will pay you $5, on the second guess $4, and so on. If you get it right on the sixth guess I will pay you nothing, on the seventh guess you owe me $1, on the eight you owe me $2, and so forth.

Q1) Should you play the game with me?

Q2) What is your expected return?

Good Luck!

 

EV of $-.417 to -$.361 is what I got. Thats assuming the optimal strategy is to just guess the middle number each time and go from there. The range exists because if theres an even number of numbers left to guess you cant chose the exact midpoint so one side is going to have one fewer options than the other if you guess wrong that turn")" />

 
Best Response

@3green - It looks like your code is missing some parantheses. Lets see if I can fix it. You're not the first person to have trouble with the code suggesting that I may be giving bad advice. Oddly, the buttons in the initial post I reference all work fine.

your original answer with the parantheses added:

and, another test with your same answer:

Let's see how this works...

"My caddie's chauffeur informs me that a bank is a place where people put money that isn't properly invested."
 

cooldurg's answer: EV of $-.417 to -$.361 is what I got. Thats assuming the optimal strategy is to just guess the middle number each time and go from there. The range exists because if theres an even number of numbers left to guess you cant chose the exact midpoint so one side is going to have one fewer options than the other if you guess wrong that turn")" />

smeethu's answer:

"My caddie's chauffeur informs me that a bank is a place where people put money that isn't properly invested."
 

Additionally log base 2 of 100 = 6.6438 giving the average guesses needed. While this may make it appear as if your average would be a negative value you need to account for the fact that this distribution terminates at 7 (the maximum number of guesses needed) but the lower extreme is 1 guess. I don't have a calculator on me, so I can't find the standard deviation (it would allow for the output of the average expected value of $.20). This is abridged/statistical method of finding the same answer as mikeswimn and I found through a manual method.

 

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