During certain 5 months, the highest month sales value is 5.

Question

During certain 5 months, the highest month sales value is 5. What is the deviation of 5 sales values?
1) Range =0
2) Mean=5

thearch · Answer

It is D.
If mean=max value it means that all values are equal and STD deviation is 0

july05 · Answer

guys, could you please give a formula (explain a little more) for Standard Deviation?

thanks.

MA · Answer

thats a blunder. :drunk

thearch · Answer

I think that all you have to know about Standard deviation is that it is a measure of dispersion around the mean value. 
If the range is 0, it means that MAX-MIN=0, or MAX value=Min Value. The deviation is obviously 0.
If the mean is = to MAX value, or = to the MIN value, then the set is composed of all equal numbers (nothing would have changed if the stem had said: "the least value is 5, and the mean is 5). 
Hope it's sufficiently clear.

Dan · Answer

thearch,

maybe I am missing something but,

if range = 0, it does not mean that SD is necessarily 0.

5 values could be: 

5,1,1,1,5 range = 0, but SD is not.
5,5,5,5,5 range = 0, SD = 0.

thearch · Answer

you're almost right.
In the first case, range is not 0, it is 4. (Max value is 5 and min value is 1)
In this case, range can be 0 only with all 5, as you say in your second example.

ian7777 · Answer

I definately agree not only with the answer, but also the approach. nice explanation.

ssap · Answer

'D'

Stmt 1 : Range = 0 -> Std = 0
Stmt 2 = Mean = 5 -> Mean = Highest sales value -> Std = 0

sparky · Answer

A very nice problem, thanks india_pb

Is 'deviation' a normal name for 'standard deviation'?

HIMALAYA · Answer

but i disagree with thearch's explanation that the range is zero if -5 is in the set. the only possible case to have zero is identical numbers.

ian7777 · Answer

Yes, you're right of course. I wasn't referring to the -5 part, actually, I glossed over that. I was referring to the fact that you don't need to be able to calculate SD, you just have to know how to use it, and to understand what role range of 0 would have in a SD problem. It definately can come up on the real exam.

thearch · Answer

Oh yes,

you're absolutely right, I think it is better to edit the post and delete such bulls**t

Antmavel · Answer

A for me

with statement 1 we already ahve the number 5 and we know that the highest value - the lowest is 0. So all number are equals. So deviation =0

with statement 2 we have the information that the mean is 5 but we only know one value for one month (5) so it can be 20,10,5,10,20 or 5,5,5,5,5 for example. Impossible to be sure of the deviation.

thearch · Answer

Hi antmavel,
probably you overlooked that the stem states that "During certain  5 months , the  highest  month sales value is 5"

Antmavel · Answer

yep indeed D

JoyLibs · Answer

Please read this thread. Some good tips statistics-rules-and-tips-69015.html

venmic · Answer

This answer has goto be D

1) The maimum value is 5
2) the remaining values su = 20 since there are 5 values
3) the only way that the remainng values can be = 20 is 5+5+5+5 since
the max value is 5
4) if any one value is less than 5 then the remaining values one of them is greater than 5 example
4 6 5 5 5 -- 6 is not possible

so therefore answer is D

A is also Suff since if in a range al the values are equal only then the SD is 0

During certain 5 months, the highest month sales value is 5.

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