Oct 18 08:00 AM PDT  09:00 AM PDT Learn an intuitive, systematic approach that will maximize your success on Fillintheblank GMAT CR Questions. Oct 19 07:00 AM PDT  09:00 AM PDT Does GMAT RC seem like an uphill battle? eGMAT is conducting a free webinar to help you learn reading strategies that can enable you to solve 700+ level RC questions with at least 90% accuracy in less than 10 days. Sat., Oct 19th at 7 am PDT Oct 20 07:00 AM PDT  09:00 AM PDT Get personalized insights on how to achieve your Target Quant Score. Oct 22 08:00 PM PDT  09:00 PM PDT On Demand for $79. For a score of 4951 (from current actual score of 40+) AllInOne Standard & 700+ Level Questions (150 questions)
Author 
Message 
TAGS:

Hide Tags

Manager
Joined: 07 Sep 2010
Posts: 249

Website W receives orders for its products every day. What is the Stan
[#permalink]
Show Tags
08 Oct 2013, 09:01
Question Stats:
70% (01:04) correct 30% (01:10) wrong based on 599 sessions
HideShow timer Statistics
Website W receives orders for its products every day. What is the Standard Deviation of the number of orders that Website W received daily for the past 5 days? (1) The Average (Arithmetic Mean) number of orders that Website W received each per day for the past 5 days is equal to the greatest of the number of orders that Website W received daily for the past 5 days. (2) The range of the number of orders that Website W received daily for the past 5 days is Zero.
Official Answer and Stats are available only to registered users. Register/ Login.




Math Expert
Joined: 02 Sep 2009
Posts: 58416

Re: Website W receives orders for its products every day. What is the Stan
[#permalink]
Show Tags
09 Oct 2013, 00:59
Website W receives orders for its products every day. What is the Standard Deviation of the number of orders that Website W received daily for the past 5 days?(1) The Average (Arithmetic Mean) number of orders that Website W received each per day for the past 5 days is equal to the greatest of the number of orders that Website W received daily for the past 5 days. Since mean=greatest, then the number of orders each day was the same. This implies that the standard deviation is 0 (the standard deviation of a set is zero if and only the set consists of identical numbers). Sufficient. (2) The range of the number of orders that Website W received daily for the past 5 days is Zero. Basically the same here: since the range is 0 (greatestsmallest=0 > greatest=smallest), then the number of orders each day was the same. Sufficient. Answer: D.
_________________




Manager
Joined: 18 Dec 2012
Posts: 94
Location: India
Concentration: General Management, Strategy
GMAT 1: 660 Q49 V32 GMAT 2: 530 Q37 V25
GPA: 3.32
WE: Manufacturing and Production (Manufacturing)

Re: Website W receives orders for its products every day. What is the Stan
[#permalink]
Show Tags
08 Oct 2013, 09:20
imhimanshu wrote: Website W receives orders for its products every day. What is the Standard Deviation of the number of orders that Website W received daily for the past 5 days? a) The Average(Arithmetic Mean) number of orders that Website W received each per day for the past 5 days is equal to the greatest of the number of orders that Website W received daily for the past 5 days. b) The range of the number of orders that Website W received daily for the past 5 days is Zero. Hi, Standard Deviation = Sum of the square of the variations from mean / total number of entities. Statement 1 : The average of number of orders = Greatest order of the day. Hence the variation = 0, so the SD = 0 Sufficient Statement 2 : Range = Max value  min value Here the range = 0 The number of orders = 0 ( Number of orders can't be negative) So SD = 0 Sufficient Both the statements are sufficient Option D Hope it is clear Cheers Qoofi
_________________
I'm telling this because you don't get it. You think you get it which is not the same as actually getting it. Get it?




Manager
Joined: 29 Aug 2013
Posts: 69
Location: United States
Concentration: Finance, International Business
GMAT 1: 590 Q41 V29 GMAT 2: 540 Q44 V20
GPA: 3.5
WE: Programming (Computer Software)

Re: Website W receives orders for its products every day. What is the Stan
[#permalink]
Show Tags
09 Oct 2013, 00:51
imhimanshu wrote: Website W receives orders for its products every day. What is the Standard Deviation of the number of orders that Website W received daily for the past 5 days? a) The Average(Arithmetic Mean) number of orders that Website W received each per day for the past 5 days is equal to the greatest of the number of orders that Website W received daily for the past 5 days. b) The range of the number of orders that Website W received daily for the past 5 days is Zero. For standard deviation you just need to know if the numbers in the sequence are in some particular order. For eg in case of consecutive numbers the deviation can be calculated. and if all the numbers in a particular sequence are same then the deviation will be 0. Statement 1: If the average of the numbers is equal to the greatest of all the numbers then all the numbers have to be that greatest number. Hence there is no deviation. eg. 3,4,5 the greatest is 5 but average is 4. So it all the numbers have to be 5 for the average to be 5. But if it were stated that the median is equal to the highest then it would have been insufficient since median can be the greatest number of those 5 days and the first 2 can be different. hence Sufficient. Statement 2: If the range is 0, then the highest number of delivery  lowest number of delivery is 0. So if the highest number in the sequence is equal to the lowest number in the sequence, all the numbers in that sequence has to be same. hence Sufficient



Intern
Joined: 06 Mar 2015
Posts: 3

Re: Website W receives orders for its products every day. What is the Stan
[#permalink]
Show Tags
13 May 2016, 22:28
Hi Bunuel,
Thanks for your crystal clear explanation. However, i have a question. If the first option is written as :'The Average (Arithmetic Mean) number of orders that Website W received each per day for the past 5 days is equal to the least of the number of orders that Website W received daily for the past 5 days', what would be the answer. I believe it would be insufficient to answer using the first option. Please comment.
Thanks, Khitindra



Math Expert
Joined: 02 Aug 2009
Posts: 7967

Re: Website W receives orders for its products every day. What is the Stan
[#permalink]
Show Tags
13 May 2016, 22:33
khitindra wrote: Hi Bunuel,
Thanks for your crystal clear explanation. However, i have a question. If the first option is written as :'The Average (Arithmetic Mean) number of orders that Website W received each per day for the past 5 days is equal to the least of the number of orders that Website W received daily for the past 5 days', what would be the answer. I believe it would be insufficient to answer using the first option. Please comment.
Thanks, Khitindra Hi khitindra, If the sentence was :'The Average (Arithmetic Mean) number of orders that Website W received each per day for the past 5 days is equal to the least of the number of orders that Website W received daily for the past 5 days since average = least, this means all the orders are same .... average can be equal to least or greatest ONLY when the orders are same... say least and average are 10, so if any orders above this would change the average so all have to be SAME
_________________



Senior SC Moderator
Joined: 14 Nov 2016
Posts: 1348
Location: Malaysia

Re: Website W receives orders for its products every day. What is the Stan
[#permalink]
Show Tags
18 May 2017, 18:03
imhimanshu wrote: Website W receives orders for its products every day. What is the Standard Deviation of the number of orders that Website W received daily for the past 5 days?
(1) The Average (Arithmetic Mean) number of orders that Website W received each per day for the past 5 days is equal to the greatest of the number of orders that Website W received daily for the past 5 days.
(2) The range of the number of orders that Website W received daily for the past 5 days is Zero. Each statement says the same thing. Range = 0. If the mean = the max, then all the numbers are the same. Try some sets of numbers to see, that will help on test day. Say the mean is 5 and the max is 5 OK, then if I have any other number in the set. Say 4, {4, 5}, mean isn't 5 any more, too small So all the numbers = 5 Answer : D
_________________
"Be challenged at EVERY MOMENT."“Strength doesn’t come from what you can do. It comes from overcoming the things you once thought you couldn’t.”"Each stage of the journey is crucial to attaining new heights of knowledge."Rules for posting in verbal forum  Please DO NOT post short answer in your post! Advanced Search : https://gmatclub.com/forum/advancedsearch/



Intern
Joined: 13 Jul 2017
Posts: 3

Re: Website W receives orders for its products every day. What is the Stan
[#permalink]
Show Tags
25 Jul 2017, 09:22
Another approach to solve this.
(1) Let's say: a<b<c<d<e Average is equal to the greatest: (a+b+c+d+e)/5=e > a+b+c+d+e=5e > a+b+c+d = 4e All elements are equal. Standard deviation is 0. Sufficient.
(2) If the range is 0 it means that all elements are equal, like in (1). So, sufficient too.
Answer: D.



Intern
Joined: 09 Oct 2016
Posts: 32

Re: Website W receives orders for its products every day. What is the Stan
[#permalink]
Show Tags
13 Oct 2017, 21:31
sophieyu0717 wrote: Web site W receives orders for its products every day. What is the standard deviation of the numbers of orders that Web Site W received daily for the past 5 days?
(1) The average (arithmetic mean) number of orders that Web Site W received per day for the past 5 days is equal to the greatest of the numbers of orders that Web Site W received daily for the past 5 days.
(2) The range of the numbers of orders that Web Site W received daily for the past 5 days is equal to 0. First, you need to understand the meaning of standard deviation. Standard deviation measures how far a certain point is from the mean. For example, let's consider the following data : (1, 2, 3, 4, 5). The the mean of these data equal (1+2+3+4+5)/5 =15/5 = 3. Now, you can see that the largest point 5 and 1 are two points from the mean. 2 and 4 are 1 point from the mean. 3 is zero point from the mean. The range of our example is equal to the large value minus the smallest value (51=4) Now, let's go back to the main question. 1 telling you that the mean is equal to the greatest number in the set ( for example if the mean is 5 then the greatest and also the smallest numbers are 5 too . This means that all of the five days have the same number of orders thus each day is 0 point from the mean. This is sufficient. 2 is talking about the range. It's telling you that the largest number is equal the smallest number. This means that all of the numbers in the five years are equal, thus each and each day is zero point from the mean. This is sufficient too.



Intern
Joined: 29 Sep 2015
Posts: 11

Re: Website W receives orders for its products every day. What is the Stan
[#permalink]
Show Tags
30 Oct 2017, 04:14
Hi Bunuel, any similar questions one could practice?



Math Expert
Joined: 02 Sep 2009
Posts: 58416

Re: Website W receives orders for its products every day. What is the Stan
[#permalink]
Show Tags
30 Oct 2017, 04:20
nikhilc11 wrote: Hi Bunuel, any similar questions one could practice? * Standard Deviation Questions from our Special Questions Directory. 20. Descriptive Statistics For more check: ALL YOU NEED FOR QUANT ! ! !Ultimate GMAT Quantitative MegathreadHope it helps.
_________________



Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 8085
Location: United States (CA)

Re: Website W receives orders for its products every day. What is the Stan
[#permalink]
Show Tags
03 Jan 2018, 11:07
imhimanshu wrote: Website W receives orders for its products every day. What is the Standard Deviation of the number of orders that Website W received daily for the past 5 days?
(1) The Average (Arithmetic Mean) number of orders that Website W received each per day for the past 5 days is equal to the greatest of the number of orders that Website W received daily for the past 5 days.
(2) The range of the number of orders that Website W received daily for the past 5 days is Zero. We need to determine the standard deviation of the numbers of orders that website W received daily for the past 5 days. Statement One Alone: The average (arithmetic mean) number of orders that website W received per day for the past 5 days is equal to the greatest of the numbers of orders that website W received daily for the past 5 days. The only way for the average of the number of orders to be equal to the greatest number of orders is if all the values are the same. Thus, the standard deviation is 0. Statement one alone is sufficient to answer the question. Statement Two Alone: The range of the numbers of orders that Web site W received daily for the past 5 days is equal to 0. Since the range is equal to zero, all the numbers of the orders are the same, and thus the standard deviation is 0. Statement two alone is sufficient to answer the question. Answer: D
_________________
5star rated online GMAT quant self study course See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews If you find one of my posts helpful, please take a moment to click on the "Kudos" button.



Manager
Joined: 14 Aug 2012
Posts: 78
Location: United States
GMAT 1: 620 Q43 V33 GMAT 2: 690 Q47 V38

Re: Website W receives orders for its products every day. What is the Stan
[#permalink]
Show Tags
03 Oct 2018, 12:46
Does statement 1 work if the mean = lowest? Same concept just the opposite extreme



Orion Director of Academics
Joined: 19 Jul 2018
Posts: 98

Re: Website W receives orders for its products every day. What is the Stan
[#permalink]
Show Tags
03 Oct 2018, 18:11
Hey bpdulog  Yes, it would still work! What you get out of the information that mean = highest number in the original statement is that all the numbers have to be the same. Think about it this way, if they were different (say the numbers were 11, 12, and 13), you could never get the mean to be equal to the highest number because it's going to be somewhere between the highest number and the lowest number. By the same logic, for the mean to be equal to the lowest number, you'd need all numbers to be equal since the mean will be somewhere between the lowest number and the highest number.
_________________
Laura Academics Aficionado  ORION GMAT selfstudy has never been more personalized or more fun. Try ORION Free!



Manager
Joined: 06 Mar 2019
Posts: 51

Re: Website W receives orders for its products every day. What is the Stan
[#permalink]
Show Tags
09 Jul 2019, 21:19
Hi Bunuel , and ScottTargetTestPrep , chetan2u , GMATNinjaI need help in understanding statement 1. What threw me off was the word GREATEST. How can you say that the average is equal to the GREATEST number of orders if all the orders received for the past 5 days are equal? When you say GREATEST, doesn't it mean that other values are supposed to be LESSER? How can you say it's GREATEST if they're all equal? What am I missing here? Thanks.



Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 8085
Location: United States (CA)

Re: Website W receives orders for its products every day. What is the Stan
[#permalink]
Show Tags
12 Jul 2019, 18:55
It might be useful to interpret “greatest” as “no other value is greater” rather than “all other values are lesser.” So, the values can all be equal. If the average is equal to the greatest number in the set, that is another way to say that all values MUST BE THE SAME. In fact there is no other possible way for the average to equal the greatest value in the set, unless all values are the same. (Note: The same thing is true if the average is equal to the smallest number in the set.)
_________________
5star rated online GMAT quant self study course See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews If you find one of my posts helpful, please take a moment to click on the "Kudos" button.




Re: Website W receives orders for its products every day. What is the Stan
[#permalink]
12 Jul 2019, 18:55






