Exam Mistakes

Question 1

That question where the variance of 10 trials was 10 x variance of one, what was going on?

Answer 1

Lit the deprivation for expectation and variance in a binomial

Recall a binomial DISTRUBTION is the the total sum of independent Bernoulli distributors

Which are special cases of binomial where n is 1 and p is p

So thr total number of success after n indepenent Bernoulli trials= the binomial distribution

So if yiu have 10 trials, then variance will be the sum of the 10 DISTRUBTION, so just 10 x variance

And this is = to npq in derivation

Question 2

What does the total score less than n mean if you role it n times

So when you get goursekf in these situations, try convert to words, and it will always be the subtraction of an extreme

Answer 2

Basically the only way for it to be less than n, is if theres on loss,

That means 1 - prob of all wins!

Question 3

Remember how does the binomial and other rsireubtions work in terms of working probabilities

Stupid mistake

Answer 3

It’s the summation of all the cases, including the order in which these cases can go

Thus your actual probability of one condition can be greater than the probability of it happening once!

Question 4

For the modulus mean + standar to mean - standard question how to do and remember key step

Answer 4

1) need to find out the standard and mean whatver find the range first!
2) now need to identify how many numbers in between the range, subtrsvt them and ADD 1 because its also including the first number DONT FORGET

3) now need to check how many numbers are actually from the ORIGINAL SEQUENCE, not assumed 1 to n
- so equate the difference +1 to the nth therm, and that will tell you how many numbers are in between

4) now multiply by the probability 1 / total n, and dine

Question 5

Alternative and actual way to do the inequality probability sigma standard modulus q

Question 6

Remember any time they give a new scenarios and ask to find a change, try write down all the possibilitesand see what’s changed

For example why e (x) gone down q? And how to determine this too

Answer 6

For that q scenario felt that no chance of 0 or 4 girls being picked, and thus the inner porbabilties would change

Look at the BEST CASE SCENARIO, if they all want to 3, then even then the new number produced wouldnt be bigger than old number

Thus can conclude e(x) will be smaller

Say this in context, that p(x=4 ) would have a much greater contribution to e(x) than p(x=0) if they were removed

Question 7

Drawing probability distribution, how to do?

Answer 7

On x axis just the different values x can take

On the y axis a relevant scale to show probability, nothing too deep

Question 8

Remember what’s the smallest value a geometric distribution can take, for notation sakes

So say I get -3 <x < 9, what would this be

Answer 8

1, not 0, so a range would look like 1 to 10

Anyways this is just less than 10, which we know how to calculate , domt worry, but just for pure notation sake, it’s not 0 to 10 it’s 1 tp 10!

1<9, and remember geometric is discrete and that ALL disturbiojs in FM are discrtet

Question 9

If they gave a data point outside of regression line and say what does this mean about regression line relationship what to say?

Answer 9

1) that they don’t fit current regression line relationship
2) therefore the regression line relationship does not hold for larger values outside the data set, and only for smaller values probably