 # Quant: Concept Checkers - Probability Concepts

1. True or false: The covariance of a random variable with itself is equal to zero. 2) Which covariance indicates the strongest relation. a) -1, b) 0, c) 15, d) 100 3) If there are 10 securities in a sample, how many unique covariance values are there? 4) If two events are independent, then the probability of event x, given event y, is equal to what? 5) If two events are mutually exclusive, the the probability of event x, given event y, is equal to what? 6) If you are selecting x items into y grouping, which counting method do you use? 7) Which counting method is essential to the bernoulli equation? 8) Which counting method will yield larger values – a combination or a permutation? Why? Answers posting in a few minutes.
1. True or false: The covariance of a random variable with itself is equal to zero. wrong - its covariance will itself is the variance 2) Which covariance indicates the strongest relation. a) -1, b) 0, c) 15, d) 100 100 3) If there are 10 securities in a sample, how many unique covariance values are there? 10*11/2 = 55 4) If two events are independent, then the probability of event x, given event y, is equal to what? P(X|Y) = P(x intersect y)/P(y) 5) If two events are mutually exclusive, the the probability of event x, given event y, is equal to what? 0 6) If you are selecting x items into y grouping, which counting method do you use? nCr for ways to selecting group of size r out of n 7) Which counting method is essential to the bernoulli equation? don’t know… none? 8) Which counting method will yield larger values – a combination or a permutation? Why? permutation since it considers all items in the set (+ question is vague)

) True or false: The covariance of a random variable with itself is equal to zero. False 2) Which covariance indicates the strongest relation. a) -1, b) 0, c) 15, d) 100 100 3) If there are 10 securities in a sample, how many unique covariance values are there? 10c2 4) If two events are independent, then the probability of event x, given event y, is equal to what? P(X/Y) ?? 5) If two events are mutually exclusive, the the probability of event x, given event y, is equal to what? 0 6) If you are selecting x items into y grouping, which counting method do you use? xCy - if order doesn’t matter xCy*y!=xPy --> if order matters 7) Which counting method is essential to the bernoulli equation? ?? 8) Which counting method will yield larger values – a combination or a permutation? Why? Permuatation = combinatio*X! Permuatation>combination

you’re right about 10c2 on #3 the way i figured is first person shakes 9 then 8 then 7 … so 9*10/2 = 45 but for some reason i started from 10 :-F don’t know what is up with #7 ?? there are no combinatorial elements in bernoulli’s equation

1. True or false: The covariance of a random variable with itself is equal to zero. False, its the variance 2) Which covariance indicates the strongest relation. a) -1, b) 0, c) 15, d) 100 100 3) If there are 10 securities in a sample, how many unique covariance values are there? 10C2, divide by 2, 4) If two events are independent, then the probability of event x, given event y, is equal to what? p(x) 5) If two events are mutually exclusive, the the probability of event x, given event y, is equal to what? P(x) 6) If you are selecting x items into y grouping, which counting method do you use? xCy 7) Which counting method is essential to the bernoulli equation? aCb 8) Which counting method will yield larger values – a combination or a permutation? Why? a combination because order doesn’t matter Answers posting in a few minutes.
1. True or false: The covariance of a random variable with itself is equal to zero. false 2) Which covariance indicates the strongest relation. a) -1, b) 0, c) 15, d) 100 -1 3) If there are 10 securities in a sample, how many unique covariance values are there? (n^2-n)/2 = 45 4) If two events are independent, then the probability of event x, given event y, is equal to what? X*Y 5) If two events are mutually exclusive, the the probability of event x, given event y, is equal to what? 1-Py (if only two events possible) 6) If you are selecting x items into y grouping, which counting method do you use? stratified 7) Which counting method is essential to the bernoulli equation? bernoulli??? 8) Which counting method will yield larger values – a combination or a permutation? Why? permutation, AB does not equal to BA

dude these questions crazy where’d you get them from??

1. True or false: The covariance of a random variable with itself is equal to zero. False: the value will be its own variance 2) Which covariance indicates the strongest relation. a) -1, b) 0, c) 15, d) 100 Trick: You cannot say unless you know the variances of the underlying values. 3) If there are 10 securities in a sample, how many unique covariance values are there? 45. The individual who posted 55 forgot to get rid of the values of covariance of each value with itself. 4) If two events are independent, then the probability of event x, given event y, is equal to what? The probability of event x 5) If two events are mutually exclusive, the the probability of event x, given event y, is equal to what? Zero. Only one event can occur 6) If you are selecting x items into y grouping, which counting method do you use? Multinomial formula 7) Which counting method is essential to the bernoulli equation? Combination formula 8) Which counting method will yield larger values – a combination or a permutation? Why? Permutation - because order matters.
1. True or false: The covariance of a random variable with itself is equal to zero. variance? 2) Which covariance indicates the strongest relation. a) -1, b) 0, c) 15, d) 100 100 3) If there are 10 securities in a sample, how many unique covariance values are there? 10c2 4) If two events are independent, then the probability of event x, given event y, is equal to what? p(x) 5) If two events are mutually exclusive, the the probability of event x, given event y, is equal to what? 0 6) If you are selecting x items into y grouping, which counting method do you use? combination 7) Which counting method is essential to the bernoulli equation? ?? 8) Which counting method will yield larger values – a combination or a permutation? Why? permutation

I’m making them up on my own. They’re sort of the culmination of studying since november and having kept track of all the things that have screwed me over at least once (or twice, or three times… I’m dense… sometimes it takes a few rounds)

mcf Wrote: ------------------------------------------------------- > 1) True or false: The covariance of a random > variable with itself is equal to zero. > False - it’s the variance > 2) Which covariance indicates the strongest > relation. a) -1, b) 0, c) 15, d) 100 > Can’t tell - Covariance has units so is not comparable > 3) If there are 10 securities in a sample, how > many unique covariance values are there? > 45 = 10*9/2 > 4) If two events are independent, then the > probability of event x, given event y, is equal to > what? > P(x) > 5) If two events are mutually exclusive, the the > probability of event x, given event y, is equal to > what? > 0 > 6) If you are selecting x items into y grouping, > which counting method do you use? > combinations > 7) Which counting method is essential to the > bernoulli equation? > The Bernoulli equation? You mean the one about air flow over a wing? > 8) Which counting method will yield larger values > – a combination or a permutation? Why? > Permutations because combinations are permutations divided by some >= 1 integer > > Answers posting in a few minutes.

For a good discussion of Bernoulli’s eqn: http://www.grc.nasa.gov/WWW/K-12/airplane/bern.html Can’t see how this is relevant to the exam, but very interesting.