It is currently 20 Nov 2017, 20:07

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Urgent - Need Help for One standard Deveiation Question

Author Message
Intern
Joined: 29 Jun 2008
Posts: 15

Kudos [?]: 2 [0], given: 0

Urgent - Need Help for One standard Deveiation Question [#permalink]

### Show Tags

12 Jul 2009, 20:42
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions

### HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

The List consist of the times in seconds that took each of the schoolchildren to run a distance of 400 meters. If the standard deveiation of the 10 running times is 22.4 seconds,rounded to the nearest tenth of a second, how many of the 10 running times are more than one standard deviation below the mean of the 10 running times?

1. One
2. Two
3. Three
4. Four
5. Five

Answer is two, but i dont know how to calcualte this one though it looks simple ... Pleae help me .. have exam in next 3 weeks.

Regards,
Puneet Pareek

Kudos [?]: 2 [0], given: 0

Current Student
Joined: 03 Aug 2006
Posts: 115

Kudos [?]: 309 [0], given: 3

Re: Urgent - Need Help for One standard Deveiation Question [#permalink]

### Show Tags

12 Jul 2009, 21:33
Puneet,

Your question is missing the list of the 10 running times in seconds. Once you have that list this is how you would proceed.

1. Calculate the mean (avg) of the 10 numbers

$$\Rightarrow \frac{N1+N2+N3+...+N8+N9+N10}{10}=N_{avg}$$

2. Subtract the SD i.e. 22.4 from the avg

$$\Rightarrow N_{avg}-SD=N_{avg}-22.4$$

Now look for running times in the list that are less than this calculated value. The answer should be the number of values that satisfy the above criteria.

Kudos [?]: 309 [0], given: 3

Intern
Joined: 29 Jun 2008
Posts: 15

Kudos [?]: 2 [0], given: 0

Re: Urgent - Need Help for One standard Deveiation Question [#permalink]

### Show Tags

14 Jul 2009, 19:27
Hi Nookway,

I got my answer... thanks a ton ... i calculated .. .answer is two only ...

Regards,
Puneet Pareek

Kudos [?]: 2 [0], given: 0

Re: Urgent - Need Help for One standard Deveiation Question   [#permalink] 14 Jul 2009, 19:27
Display posts from previous: Sort by