HELP! Any statisticians out there?

hailzp

I am doing my stats assignment and I find the theory chapter very difficult.

The question is: The owner of a book store has analysed the sales data from customers over the last year and found that the mean amount of money spent by a customer is $21.45 with a standard deviation of $17.87.

a) Using only the statistical information above, briefly explain why X is not Normally distributed.

b) In fact, the distribution of X is strongly skewed. Would X be positively skewed or negatively skewed? Justify your answer.


PLEASE help me if you can. I am tearing my hair out

Carl01

It is a flashback to high school!!

hailzp

The **** news is, is this a uni course!!! I have to do it for psychology. My brain finds it very difficult to work this way.

xcrushx28

I am doing my stats assignment and I find the theory chapter very difficult.

The question is: The owner of a book store has analysed the sales data from customers over the last year and found that the mean amount of money spent by a customer is $21.45 with a standard deviation of $17.87.

a) Using only the statistical information above, briefly explain why X is not Normally distributed.

b) In fact, the distribution of X is strongly skewed. Would X be positively skewed or negatively skewed? Justify your answer.


PLEASE help me if you can. I am tearing my hair out

Well I only took one statistic class so I'm no expert, but that's a very huge standard deviation..... That's why its not normally distributed. Think if you added two or subtracted two standard deviations from your mean.

Probably positively skewed and I don't have any reasoning for that.....

Not sure if I'm helping at this point Google?

bigdawg025

I really want to help... but I'd have to dig in my business stats book from last semester to give you a good answer. I know the standard deviation is extremely high in comparison to the mean meaning there are several extreme data in the sample used. This would be why it's not normally distributed.

I don't have a clue about part b... because I would think the standard deviation could apply to either end... probably positively skewed, though.

hailzp

OK guys. Good so far, gives me a base to work from. I tried googling stuff but it is a bit difficult if your not really sure what you are looking for :frown:

xcrushx28

So you could say that in relation to the mean the standard deviation is very high and thus cannot be normalized.

Its positively skewed because the actual deviation should be much lower.

HotBodUnderConstruction

I think it has to do with the fact that the distribution is truncated at 0. In other words, nobody in the store's sales data will be recorded as spending negative dollars...thus the distribution will be heavily skewed to the left...the size of the standard deviation is not relevant for this question.

j4nash

Standard deviation is extremely high relative to the mean.. this would imply skewness.

I don't think the negative or postiive skew can be derived without a sample as a positive skew and a negative skew can both have the same mean and standard deviation.

but it's been 10 yrs.

zipnguyen

I am doing my stats assignment and I find the theory chapter very difficult.

The question is: The owner of a book store has analysed the sales data from customers over the last year and found that the mean amount of money spent by a customer is $21.45 with a standard deviation of $17.87.

a) Using only the statistical information above, briefly explain why X is not Normally distributed.

b) In fact, the distribution of X is strongly skewed. Would X be positively skewed or negatively skewed? Justify your answer.


PLEASE help me if you can. I am tearing my hair out

Wow, really on MFP? Well Xbar is 21.45 with 1 std dev of 17.87. So if 99% of all oberservations fall within 3 std dev, then 17.87*3=upper and lower range of said 99%. Note how when you multiply 3*17.87 you get something close to $48. So how can sales of books be $21.45-$48= some negative number when supposedly all 99% of oberservations is supposed to occur within 3 std dev and assumed in business to be a positive number.

Oh, btw the way, I have a Ph.D. In finance and BA and MA in applied economics and statistics. :bigsmile:

Can't give you the answer but the hint above pretty much solved the problem for you... Of skewness, etc.

zipnguyen

You know how hard it is to type with thumbs...

nikolaim5

DOh!

hailzp

You know how hard it is to type with thumbs...

(Yus, really, on MFP, I have no where else to go ): )

I don't doubt your academic achievements! Thank you very much, helped a lot. :bigsmile:

zipnguyen

You know how hard it is to type with thumbs...

(Yus, really, on MFP, I have no where else to go ): )

I don't doubt your academic achievements! Thank you very much, helped a lot. :bigsmile:

Good luck.

luv_lea

The answer is C, always choose C. Or, at least that's what I always did in high school when I didn't know the answer.

significance

What percent of customers would have to have a negative spend (less than zero $) if it were normally skewed, with that standard deviation?

nnylee

I'm not a statistician or anything near to that, but I think it's so cool that you actually got answers here.

caveats

Wow, really on MFP? Well Xbar is 21.45 with 1 std dev of 17.87. So if 99% of all oberservations fall within 3 std dev, then 17.87*3=upper and lower range of said 99%. Note how when you multiply 3*17.87 you get something close to $48. So how can sales of books be $21.45-$48= some negative number when supposedly all 99% of oberservations is supposed to occur within 3 std dev and assumed in business to be a positive number.

Oh, btw the way, I have a Ph.D. In finance and BA and MA in applied economics and statistics. :bigsmile:

Can't give you the answer but the hint above pretty much solved the problem for you... Of skewness, etc.

Damn, I could've used your "help" last week at work when we were compiling reports for a client in Excel since we're waiting on a new SPSS license from corporate. >_<

karagav

this scares me...i'm just starting the stats portion of my research and statistics course...i ended the research methods term with a 93 and nottttt so sure this semester is going to be such a happy ending!! haha

becoming_a_new_me

I am doing my stats assignment and I find the theory chapter very difficult.

The question is: The owner of a book store has analysed the sales data from customers over the last year and found that the mean amount of money spent by a customer is $21.45 with a standard deviation of $17.87.

a) Using only the statistical information above, briefly explain why X is not Normally distributed.

b) In fact, the distribution of X is strongly skewed. Would X be positively skewed or negatively skewed? Justify your answer.


PLEASE help me if you can. I am tearing my hair out

Wow, really on MFP? Well Xbar is 21.45 with 1 std dev of 17.87. So if 99% of all oberservations fall within 3 std dev, then 17.87*3=upper and lower range of said 99%. Note how when you multiply 3*17.87 you get something close to $48. So how can sales of books be $21.45-$48= some negative number when supposedly all 99% of oberservations is supposed to occur within 3 std dev and assumed in business to be a positive number.

Oh, btw the way, I have a Ph.D. In finance and BA and MA in applied economics and statistics. :bigsmile:

Can't give you the answer but the hint above pretty much solved the problem for you... Of skewness, etc.

You have a PhD aaaaaand you look like that? Well, you can solve my problems anytime. :blushing: :laugh:

hailzp

Well guys, you have all been outstanding. Assignment completed. I may have to come back to the forums next week

zipnguyen

I am doing my stats assignment and I find the theory chapter very difficult.

The question is: The owner of a book store has analysed the sales data from customers over the last year and found that the mean amount of money spent by a customer is $21.45 with a standard deviation of $17.87.

a) Using only the statistical information above, briefly explain why X is not Normally distributed.

b) In fact, the distribution of X is strongly skewed. Would X be positively skewed or negatively skewed? Justify your answer.


PLEASE help me if you can. I am tearing my hair out

Wow, really on MFP? Well Xbar is 21.45 with 1 std dev of 17.87. So if 99% of all oberservations fall within 3 std dev, then 17.87*3=upper and lower range of said 99%. Note how when you multiply 3*17.87 you get something close to $48. So how can sales of books be $21.45-$48= some negative number when supposedly all 99% of oberservations is supposed to occur within 3 std dev and assumed in business to be a positive number.

Oh, btw the way, I have a Ph.D. In finance and BA and MA in applied economics and statistics. :bigsmile:

Can't give you the answer but the hint above pretty much solved the problem for you... Of skewness, etc.

You have a PhD aaaaaand you look like that? Well, you can solve my problems anytime. :blushing: :laugh:

Yes ma'am

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> http://www.ratemyprofessors.com/ShowRatings.jsp?tid=334783

becoming_a_new_me

I am doing my stats assignment and I find the theory chapter very difficult.

The question is: The owner of a book store has analysed the sales data from customers over the last year and found that the mean amount of money spent by a customer is $21.45 with a standard deviation of $17.87.

a) Using only the statistical information above, briefly explain why X is not Normally distributed.

b) In fact, the distribution of X is strongly skewed. Would X be positively skewed or negatively skewed? Justify your answer.


PLEASE help me if you can. I am tearing my hair out

Wow, really on MFP? Well Xbar is 21.45 with 1 std dev of 17.87. So if 99% of all oberservations fall within 3 std dev, then 17.87*3=upper and lower range of said 99%. Note how when you multiply 3*17.87 you get something close to $48. So how can sales of books be $21.45-$48= some negative number when supposedly all 99% of oberservations is supposed to occur within 3 std dev and assumed in business to be a positive number.

Oh, btw the way, I have a Ph.D. In finance and BA and MA in applied economics and statistics. :bigsmile:

Can't give you the answer but the hint above pretty much solved the problem for you... Of skewness, etc.

You have a PhD aaaaaand you look like that? Well, you can solve my problems anytime. :blushing: :laugh:

Yes ma'am

---

> http://www.ratemyprofessors.com/ShowRatings.jsp?tid=334783

I 1001% completely agree with the chili pepper rating

zipnguyen

Wow, really on MFP? Well Xbar is 21.45 with 1 std dev of 17.87. So if 99% of all oberservations fall within 3 std dev, then 17.87*3=upper and lower range of said 99%. Note how when you multiply 3*17.87 you get something close to $48. So how can sales of books be $21.45-$48= some negative number when supposedly all 99% of oberservations is supposed to occur within 3 std dev and assumed in business to be a positive number.

Oh, btw the way, I have a Ph.D. In finance and BA and MA in applied economics and statistics. :bigsmile:

Can't give you the answer but the hint above pretty much solved the problem for you... Of skewness, etc.

Damn, I could've used your "help" last week at work when we were compiling reports for a client in Excel since we're waiting on a new SPSS license from corporate. >_<

LOL @ SPSS. Why not SAS or stick with Excel with VBAStatpak.

zipnguyen

Yes ma'am

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> http://www.ratemyprofessors.com/ShowRatings.jsp?tid=334783


I 1001% completely agree with the chili pepper rating

Wife sat in my class once and asked me out to lunch posing as a student. Other students were shocked as heck that I'd go out with a student. :laugh:

That little gag only works during the first week of school or so, which is next week...

Mmmporkrinds

42?

caveats

LOL @ SPSS. Why not SAS or stick with Excel with VBAStatpak.

Because corporate likes SPSS, and we're at the mercy of their bean-counters. :sick: (No offense to any present.) Although earlier today, our VP threatened me with R ...

Just an interesting dynamic re: purchasing at work because we're an American business unit (kind of small, ~26 employees) of a Canadian corporate parent. The Canadians seem to forget they acquired some Americans along the way ...

zipnguyen

this scares me...i'm just starting the stats portion of my research and statistics course...i ended the research methods term with a 93 and nottttt so sure this semester is going to be such a happy ending!! haha

good luck to you too

zipnguyen

LOL @ SPSS. Why not SAS or stick with Excel with VBAStatpak.

Because corporate likes SPSS, and we're at the mercy of their bean-counters. :sick: (No offense to any present.) Although earlier today, our VP threatened me with R ...

Just an interesting dynamic re: purchasing at work because we're an American business unit (kind of small, ~26 employees) of a Canadian corporate parent. The Canadians seem to forget they acquired some Americans along the way ...

:laugh: Still laughing about this

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>SPSS

HotBodUnderConstruction

LOL @ SPSS. Why not SAS or stick with Excel with VBAStatpak.

Because corporate likes SPSS, and we're at the mercy of their bean-counters. :sick: (No offense to any present.) Although earlier today, our VP threatened me with R ...

Just an interesting dynamic re: purchasing at work because we're an American business unit (kind of small, ~26 employees) of a Canadian corporate parent. The Canadians seem to forget they acquired some Americans along the way ...

:laugh: Still laughing about this

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>SPSS

You can do a lot more with R, in my opinion. It's less user-friendly than STATA but fantastic once you get the hang of it.

zipnguyen

Statistical Package for Social Sciances. Is it even the real edition or the "student" version that your company is using. I only ask because I have clients that do this mainly because it's simplistic in nature as opposed to more in depth analytical tools. There's always Soritech, but that maybe too hard to use if your firm is used to SPSS.