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Re: Criminals released from prison on parole have generally been put under
[#permalink]
08 May 2015, 09:11
08 May 2015, 09:11
Ok, let's play some maths with this CR for a clearer picture.
1) The percentage of released criminals arrested while under intensive supervision = a/b , whereas a = number of re-arrested, b = number of released criminals under supervision
2) The percentage of released criminals arrested while under routine supervision = c/d , whereas c = number of re-arrested, d = number of released criminals under supervision
Based on one premise, we have a/b = c/d
3) Now read the conclusion again "so intensive supervision is no more effective than routine supervision in preventing criminals from committing additional crimes. " , we have x/ b >= y/ d , whereas x = number of additional crimes committed by criminals under intensive supervision, y = number of additional crimes committed by criminals under routine supervision
4) Now we look at C to see why it's the assumption. C reads " The proportion of arrests to crimes committed was not significantly higher for criminals under intensive supervision than those under routine supervision.",
arrests to crimes = re-arrested / number of additional crimes = a/x or c/y
C means a/x not much > c/y
Negating C means a/x >> c/y . , we have a/b = c/d based on premise, then (a/b) / (a/x) << (c/d) / (c/y) <=> x/b << y/d , which is the opposite of conclusion. Thus, C must be the assumption here.
1) The percentage of released criminals arrested while under intensive supervision = a/b , whereas a = number of re-arrested, b = number of released criminals under supervision
2) The percentage of released criminals arrested while under routine supervision = c/d , whereas c = number of re-arrested, d = number of released criminals under supervision
Based on one premise, we have a/b = c/d
3) Now read the conclusion again "so intensive supervision is no more effective than routine supervision in preventing criminals from committing additional crimes. " , we have x/ b >= y/ d , whereas x = number of additional crimes committed by criminals under intensive supervision, y = number of additional crimes committed by criminals under routine supervision
4) Now we look at C to see why it's the assumption. C reads " The proportion of arrests to crimes committed was not significantly higher for criminals under intensive supervision than those under routine supervision.",
arrests to crimes = re-arrested / number of additional crimes = a/x or c/y
C means a/x not much > c/y
Negating C means a/x >> c/y . , we have a/b = c/d based on premise, then (a/b) / (a/x) << (c/d) / (c/y) <=> x/b << y/d , which is the opposite of conclusion. Thus, C must be the assumption here.
Re: Criminals released from prison on parole have generally been put under
[#permalink]
04 Jul 2015, 23:59
04 Jul 2015, 23:59
Hello,
Can anyone comments about point raised by
andymann.
I am also on same page.
I think, the only reason (D) is incorrect is because it restricts the "sample space" to "criminals under intensive supervision.
Looking for expert reply.
Thanks
Vikas
Can anyone comments about point raised by
andymann.
I am also on same page.
I think, the only reason (D) is incorrect is because it restricts the "sample space" to "criminals under intensive supervision.
Looking for expert reply.
Thanks
Vikas
Re: Criminals released from prison on parole have generally been put under
[#permalink]
09 Jul 2015, 23:32
09 Jul 2015, 23:32
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Expert Reply
earnit wrote:
VeritasPrepKarishma wrote:
souvik101990 wrote:
Criminals released from prison on parole have generally been put under routine supervision. A recent program has allowed criminals to leave prison early under intensive supervision; they must obey curfews and in some cases they must be electronically monitored. The percentage of released criminals arrested while under supervision is the same for intensive supervision as for routine supervision, so intensive supervision is no more effective than routine supervision in preventing criminals from committing additional crimes.
Which one of the following is an assumption on which the argument relies?
(A) The criminals under intensive supervision, but not those under routine supervision, were required to work or attend school during their supervision period.
(B) All of the criminals who were arrested while under routine supervision had been in prison more than once before being paroled and put under supervision.
(C) The proportion of arrests to crimes committed was not significantly higher for criminals under intensive supervision than those under routine supervision.
(D) Of the criminals arrested while under intensive supervision, some would not have committed crimes if they had been under routine supervision.
(E) The number of criminals put under routine supervision was not significantly greater than the number of criminals put under intensive supervision.
Which one of the following is an assumption on which the argument relies?
(A) The criminals under intensive supervision, but not those under routine supervision, were required to work or attend school during their supervision period.
(B) All of the criminals who were arrested while under routine supervision had been in prison more than once before being paroled and put under supervision.
(C) The proportion of arrests to crimes committed was not significantly higher for criminals under intensive supervision than those under routine supervision.
(D) Of the criminals arrested while under intensive supervision, some would not have committed crimes if they had been under routine supervision.
(E) The number of criminals put under routine supervision was not significantly greater than the number of criminals put under intensive supervision.
Responding to a pm:
Premises:
Criminals released on parole are put under routine supervision.
A recent program allows criminals to leave prison early under intensive supervision;
The percentage of re-arrests is same for intensive supervision as well as for routine supervision.
Conclusion:
intensive supervision is no more effective than routine supervision in preventing criminals from committing additional crimes
The key word is highlighted. We are saying that since both types of supervision result in the same percentage of re-arrests, it means both have the same success rate in preventing crimes. There is a gap in this logic. Based on the number of re-arrests (which is same for both), we are assuming the number of crimes committed are the same under both types of supervision. What if, number of crimes committed is much higher under routine supervision but re-arrests are rarer? Then can we say that both methods are equally effective in preventing crimes? No. So option (C) is an assumption. It says that the proportion of arrests to crimes committed was similar in both.
On the other hand, (E) doesn't affect our argument. The number put under each is of no consequence to us. We are comparing percentages. Since their percentages are similar, we can certainly compare their effectiveness even if the number of criminals is different.
Answer (C)
VeritasPrepKarishma,
Just need a bit of clarity on the highlighted portion: It says that we are assuming that no. of crimes committed are same under both types of supervision.
Please correct me, if i am wrong but are we not assuming that the PROPORTION of re-arrests to crimes committed is same for both types of supervision.
\(Re-arrests/Crimes Committed\) for Intense Supervision = \(Re-arrests/Crimes Committed\) for Routine Supervision
We are given that the Percentage of re-arrests is same under both types of supervision but that doesn't mean that the number of re-arrests is same, right?
And by that logic, we can conclude that the two ratios must be equal, hence the same proportion but not necessarily have the same numbers.
For ex: re-arrests to no. of crimes committed proportion for both routine and intense supervision respectively-:
\(3/5 = 6/10\)
So, here the number of crimes committed are different, yet the two ratios are equal.
Please clarify.
Thank you.
We are given that the percentage of re-arrests is the same. This means that if 100 people each were released under the two systems, in both cases there were say, 10 re-arrests. (So 10% re-arrests in both cases) - This is given.
But to arrive at the conclusion, we are assuming that the percentage of crimes committed was the same in both cases. So if 100 people were released under each program, we need to assume that the same number committed crimes in both cases to be able to say that "intensive supervision is no more effective than routine supervision in preventing criminals from committing additional crimes".
Point is that the argument gives the link between re-arrests and criminals released. But it draws conclusion of the link between re-arrests and the actual number of crimes. The argument tells us nothing about the actual number of crimes. The actual number of crimes could have been very different in the two cases. Perhaps 30 of the people released under routine supervision committed crimes again but only 10 got re-arrested... On the other hand, only 15 of the people released under intense supervision committed crimes again and 10 got re-arrested. We are assuming that this is not the case to conclude that "intensive supervision is not more effective".
