Solved

Math question

Posted on 2016-10-07
3
76 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
3 Comments
 
LVL 40

Accepted Solution

by:
Kyle Abrahams earned 500 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

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

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

Suggested Solutions

Title # Comments Views Activity
How to onstruct a table 4 47
Relative Frequency Distribution 4 30
Probability Distribution 5 43
Discrete Values 2 47
Article by: Nadia
Linear search (searching each index in an array one by one) works almost everywhere but it is not optimal in many cases. Let's assume, we have a book which has 42949672960 pages. We also have a table of contents. Now we want to read the content on p…
Lithium-ion batteries area cornerstone of today's portable electronic devices, and even though they are relied upon heavily, their chemistry and origin are not of common knowledge. This article is about a device on which every smartphone, laptop, an…
Along with being a a promotional video for my three-day Annielytics Dashboard Seminor, this Micro Tutorial is an intro to Google Analytics API data.
This is a video describing the growing solar energy use in Utah. This is a topic that greatly interests me and so I decided to produce a video about it.

861 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

Need Help in Real-Time?

Connect with top rated Experts

25 Experts available now in Live!

Get 1:1 Help Now