The Members of the newest recruiting class of an organization are taking their physical test and those who score in the bottom 16 % will have to retest. If the scores are distributed normally and have an arithmetic mean of 72, what is the score at or below which the recruits will have to retest?
1.) there are 500 recruits in the class.
2.) 10 recruits scored 82 or higher.
Kindly help
Tough DS Question Pls help
This topic has expert replies
- dhanda.arun
- Senior | Next Rank: 100 Posts
- Posts: 52
- Joined: Thu Jul 31, 2008 12:30 pm
- Thanked: 5 times
-
- Legendary Member
- Posts: 1153
- Joined: Wed Jun 20, 2007 6:21 am
- Thanked: 146 times
- Followed by:2 members
I think the answer is Cdhanda.arun wrote:The Members of the newest recruiting class of an organization are taking their physical test and those who score in the bottom 16 % will have to retest. If the scores are distributed normally and have an arithmetic mean of 72, what is the score at or below which the recruits will have to retest?
1.) there are 500 recruits in the class.
2.) 10 recruits scored 82 or higher.
Kindly help
I used 68-95-99.8 rule for normal distribution.
mean is 72
Statement I & II clearly alone are insufficient.
Combining I & II
We have to find the SD to find the score.
recruits = 500
10 recruits have scored 82 and higher
1000/500 = 2% of recruits have scored 82 or higher.
2% is 72+3SD = 82 => 3SD=10, SD=10/3=3.33
bottom 16% will have to take the retest
72 - 3.33 = 68.77-72 1st SD 34%
68.66-3.33 = 65.33-68.66 2nd SD 14%
65.33-3.33= 62-65.33 3rd SD 2%
bottom 16% = 68.66 or below
Hence C is the answer.
-
- Legendary Member
- Posts: 1153
- Joined: Wed Jun 20, 2007 6:21 am
- Thanked: 146 times
- Followed by:2 members
First statement only gives us the no. of recruits. Nothing about below scores or top scores. Insufficient.hengirl03 wrote:Why are statements I and II insufficient?
Second statement only gives us the top scores and percentage, we dont know anything about sample space i.e. number of recruits.
Hope its clear.
- dhanda.arun
- Senior | Next Rank: 100 Posts
- Posts: 52
- Joined: Thu Jul 31, 2008 12:30 pm
- Thanked: 5 times
Thanks for the solution.
I still have some doubts:-
1.) what is 68-95-99.8 rule for normal distribution?
2.) How we deduce that 82 is third standard deviation?
I still have some doubts:-
1.) what is 68-95-99.8 rule for normal distribution?
2.) How we deduce that 82 is third standard deviation?
-
- Legendary Member
- Posts: 1153
- Joined: Wed Jun 20, 2007 6:21 am
- Thanked: 146 times
- Followed by:2 members
This link will give you a clear idea about the rule.dhanda.arun wrote:Thanks for the solution.
I still have some doubts:-
1.) what is 68-95-99.8 rule for normal distribution?
2.) How we deduce that 82 is third standard deviation?
https://en.wikipedia.org/wiki/68-95-99.7_rule
Also refer to the below post where I have explained in detail about the rule.
https://www.beatthegmat.com/pr-4-standar ... 16015.html
let me know if you still have any doubts.
- dhanda.arun
- Senior | Next Rank: 100 Posts
- Posts: 52
- Joined: Thu Jul 31, 2008 12:30 pm
- Thanked: 5 times