Still celebrating National IT Professionals Day with 3 months of free Premium Membership. Use Code ITDAY17

x
?
Solved

Math question

Posted on 2016-10-07
3
Medium Priority
?
155 Views
Last Modified: 2016-10-07
Can you please tell me why the calculations are wrong?

screenshot.PNGCORRECT ANSWER IS B

The 1st person can pick anyone. the remaining 3 must each pick the same person, with Pr = 1/5,
thus by the multiplicative principle,
indicated Pr = (1/5)³ = 1/125= 0.008000
0
Comment
Question by:Tommy Anderson
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
3 Comments
 
LVL 40

Accepted Solution

by:
Kyle Abrahams earned 2000 total points
ID: 41834108
you're ignoring the first choice.  

it's pr (1/5) ^ 4

Simplify it down to two witnesses.

By your logic the first one chooses anyone, and it's only the second guy that counts.

Not the case.

It's the probability that the first guy picks the person AND the second guy picks the same person.  (1/5 * 1/5)
1
 
LVL 27

Expert Comment

by:d-glitch
ID: 41834166
This is another horrible ambiguous question:  
Does "same person" in the last sentence refer to "same man" in the first sentence?

Ignore the first part of the problem.  Each of 4 witnesses has a choice of 5 suspects.  
So there are 54 = 625 possible ways for them to vote.

In 5 of those cases they will be voting for the same person.  There is really no other way to phrase it.
And so the probability of this happening is   5/625  =  1/125  =  0.008
2
 
LVL 32

Expert Comment

by:phoffric
ID: 41834315
I like d-glitch's response, and I was puzzled at first at the Answer B.

But then I had to think about the practical nature of lineups where my total understanding comes from watching TV shows. In every TV show I watched where there is a lineup of 5 men, the detectives believe there is one person that committed the crime. Call him person A. In other words, in the practical nature of a lineup, the same man refers to a specific man that the detectives had in mind.

Then the 4 witnesses vote (in our example, randomly). As d-glitch said, there are 5^4 = 625 possible ways for them to vote. But only in one case will they have all voted for man A. And that leads to an answer of 1/625 = 0.0016.

I reluctantly have to agree with the Answer B.
1

Featured Post

What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Article by: Nadia
Suppose you use Uber application as a rider and you request a ride to go from one place to another. Your driver just arrived at the parking lot of your place. The only thing you know about the ride is the license plate number. How do you find your U…
Article by: Nicole
This is a research brief on the potential colonization of humans on Mars.
Finds all prime numbers in a range requested and places them in a public primes() array. I've demostrated a template size of 30 (2 * 3 * 5) but larger templates can be built such 210  (2 * 3 * 5 * 7) or 2310  (2 * 3 * 5 * 7 * 11). The larger templa…
I've attached the XLSM Excel spreadsheet I used in the video and also text files containing the macros used below. https://filedb.experts-exchange.com/incoming/2017/03_w12/1151775/Permutations.txt https://filedb.experts-exchange.com/incoming/201…
Suggested Courses

715 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question