Answers to Question 29 (1 Viewer)

[hjhj]

Hi Guys! okay so this is what i got for Question 29 and I was just wondering if they were about what you got-ish...

29a) W=8, err took me foreverrr

29b)i) hmm tricky to use the one with the S or the funny symbol, i guessed and used the funny symbol one (which i think is population std dev.) so Std Dev= 5.2

29)b)ii) okay so even if that^ was wrong i can probably still get full marks in this question because thats what BOS does (lovely really) so for this i got she needed to get 58.9 to maintain her thang. I think the official answer was 59.7, so very close but just messed up a bit because of part i.

29)c)bloody mary and her website... i got that she needed 4 numerals, but i was rushing so maybe wrong...

29)d) -$1.50, i think this is right, because 1/4 for HH, 1/4 for TT, and 1/2 for HT/TH and minus $4

29)e) Present Value Formula, no Jack can't repay loan in 20 years he was about $285000, so around about 14-15000 off the target

So PLEASE tell me if these look about right... or what you got!

Thanks! (a skipping face, marvellous)

 

[DJ696]

Hi Guys! okay so this is what i got for Question 29 and I was just wondering if they were about what you got-ish...

29a) W=8, err took me foreverrr

29b)i) hmm tricky to use the one with the S or the funny symbol, i guessed and used the funny symbol one (which i think is population std dev.) so Std Dev= 5.2

29)b)ii) okay so even if that^ was wrong i can probably still get full marks in this question because thats what BOS does (lovely really) so for this i got she needed to get 58.9 to maintain her thang. I think the official answer was 59.7, so very close but just messed up a bit because of part i.

29)c)bloody mary and her website... i got that she needed 4 numerals, but i was rushing so maybe wrong...

29)d) -$1.50, i think this is right, because 1/4 for HH, 1/4 for TT, and 1/2 for HT/TH and minus $4

29)e) Present Value Formula, no Jack can't repay loan in 20 years he was about $285000, so around about 14-15000 off the target

So PLEASE tell me if these look about right... or what you got!

Thanks! (a skipping face, marvellous)

Answer to question 29(e) I used the present value formula and got 251056.96 with normal repayments.
Then added 250 x 12 x 20 = 60,000 dollars.
Then add them to together 60,000 + 251056.96 = 311056.96.
311056 - 300,000 = 11056
So he could pay of the loan within 20 years

 

[hjhj]

Answer to question 29(e) I used the present value formula and got 251056.96 with normal repayments.
Then added 250 x 12 x 20 = 60,000 dollars.
Then add them to together 60,000 + 251056.96 = 311056.96.
311056 - 300,000 = 11056
So he could pay of the loan within 20 years

hmm yeah this is tricky, because its either a) adding the extra $250 to the monthly repayments (which is what I did) (and I'm leaning towards this method, because it says in the question that the MINIMUM payment is $1798.65, so i thought well thats indicating that his extra money would be added to that) and then option b) which is just adding on 250x12x20= $60000. And the two answers are so different... and i don't even understand it because how can option a not reach the target but option b does when they are paying back the same amount of money (maybe, sort of) anyway bloody annuities have me confused, for the last time... :/

Thanks for your comment though, i guess we will have to wait and see

 

[Pete15551]

They are all right. Except I'm not sure if we were suppose to round up for B) ii.... I got 59.7 or 59.8, but i rounded it to 60. So i hope i get the mark.

 

[uart]

29b)i) hmm tricky to use the one with the S or the funny symbol, i guessed and used the funny symbol one (which i think is population std dev.) so Std Dev= 5.2

29)b)ii) okay so even if that^ was wrong i can probably still get full marks in this question because thats what BOS does (lovely really) so for this i got she needed to get 58.9 to maintain her thang. I think the official answer was 59.7, so very close but just messed up a bit because of part i.

Yes, if you used the population standard deviation (sigma) then you should have ended up with a Z-score of about -1.25 and a rounded mark of 59 in part ii. If however you used the sample standard deviation (S) then you should have ended up with a Z-score of about -1.18 and a rounded mark of 60.

I can definitely understand people wanting to use the population standard deviation here, as the data set was the *entire* class, however the sample standard deviation was the correct one in this case. When we are using the standard deviation to make statistical inferences, then the sample standard deviation is almost always the correct one to use. In essence we are considering the class to be a sample of a larger (normally distributed) hypothetical population in order to make this statistical inference.

So using the sample standard deviation is technically the most correct method, but to be honest if I was marking this I’d award full marks whichever standard deviation type chosen, so long as it was correctly used to calculate the Z-score in part ii.

 

[moocow920]

Answer to question 29(e) I used the present value formula and got 251056.96 with normal repayments.
Then added 250 x 12 x 20 = 60,000 dollars.
Then add them to together 60,000 + 251056.96 = 311056.96.
311056 - 300,000 = 11056
So he could pay of the loan within 20 years

I used the graphics calculator with a repayment of the original minimum payment + $250 and found that it would take 21.something years to reach 0. I might be wrong but I think the reason your answer is so different is because you are not including the interest on the $250 each month, because remember after the $2 thousand and whatever it was payment each month, interest is calculated on the balance and the balance will increase again