HELP! Any statisticians out there?
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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=3347830 -
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 rating0 -
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.0 -
Yes ma'am
> 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...0 -
42?0
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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 ...0 -
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 too0 -
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
>SPSS0 -
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
>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.0 -
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.0
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All in good fun though. If they are used to it. Great. I still use old MS Office. 97, no joke...0
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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.
Parent does $2B in annual revenue and is hands-tied to shareholders. It's the real edition.
In fact, we're SUPPOSED to have access to the Business Intelligence and Customer Intelligence units up in the Great White North, but so far they have been very slow and unresponsive to our attempts to work with them on data analytics (while we have live clients ticking in the wings waiting for reports and recommendations). Hence, our request to acquire JUST ONE license. In all honesty, given that our license request has sat for 2 weeks, we are half-seriously considering other options.
(You wouldn't believe the *kitten* fit they threw when we requested consulting work on our Salesforce.com account ... sigh.
"You realize the consultants cost $150/hour, right?"
"Well, we realize they aren't cheap."
"So do you really need them?"
"Do you really want us to meet our sales goals this year?")
Apparently, we DID at one point have an honest-to-God data analyst in our office, but since we fired him 2 months later (after spending months recruiting him out of New York), he left and took the computer with SPSS with him ... but this was before my time (and like 2 company banks ago, so no one can track down how the license was paid to recover it), so I cannot vouch for the veracity of said story. :laugh:
Ah,what are we office peons without work drama.0 -
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.
Parent does $2B in annual revenue and is hands-tied to shareholders. It's the real edition. In fact, we're SUPPOSED to have access to the Business Intelligence and Customer Intelligence units up in the Great White North, but so far they have been very slow and unresponsive to our attempts to work with them on data analytics (while we have live clients ticking in the wings waiting for reports and recommendations). Hence, our request to acquire JUST ONE license. In all honesty, given that our license request has sat for 2 weeks, we are half-seriously considering other options.
(You wouldn't believe the *kitten* fit they threw when we requested consulting work on our Salesforce.com account ... sigh.
"You realize the consultants cost $150/hour, right?"
"Well, we realize they aren't cheap."
"So do you really need them?"
"Do you really want us to meet our sales goals this year?")
Apparently, we DID at one point have an honest-to-God data analyst in our office, but since we fired him 2 months later (after spending months recruiting him out of New York), he left and took the computer with SPSS with him ... but this was before my time (and like 2 company banks ago, so no one can track down how the license was paid to recover it), so I cannot vouch for the veracity of said story. :laugh:
Ah,what are we office peons without work drama.
Oh my bad, it's just not a software problem...:laugh:0 -
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.
Speaking as a math teacher (geometry, abstract algebra, and history of math -- definitely *not* statistics), I want to point out the thought process here because it's really useful and might help you with other questions later in the course.
You're asked to show something -- in this case, that the distribution is *not normal.*
Ask yourself, what if it were? If you can explain why that is impossible and/or doesn't make any sense, then you've established the thing you were after. So here, as this poster said, and someone else on the thread said in different words, you observe that if this were a normal distribution you'd have lots of people spending negative money. I suppose this isn't impossible, since a store probably records returns as negative expenditures, but a high percentage is very unlikely, and so you can conclude that this data is not from a normal distribution.
This is a semi-formal version of a proof by contradiction. Mathematicians use them a lot, although purists sometimes object. Sophomore/junior math majors, who are just learning to do mathematical proofs, love this strategy because it's fairly easy to wrap your mind around. We do this kind of reasoning informally all the time. Any time someone responds to a question by saying, "Well, this must be the case, because otherwise...," they are thinking this way.
I wanted to point this out because I'm willing to bet that a text that asked the question you posed here will expect you to do more of this kind of reasoning. If you're conscious of the process involved, you're more likely to see your way through the next one. Good luck!0 -
42?
:laugh:0 -
Oh my bad, it's just not a software problem...:laugh:
The world would be a lot simpler then. And probably a lot more boring. :laugh: (No offense to the software guys, either ... I'm a former journalist, okay? We're equal opportunity offenders :bigsmile: )I wanted to point this out because I'm willing to bet that a text that asked the question you posed here will expect you to do more of this kind of reasoning. If you're conscious of the process involved, you're more likely to see your way through the next one. Good luck!
I like the different approach to reasoning you brought to the discussion (and returning the thread to its original purpose :blushing: ). Also support this viewpoint because learning the textbook is a lot different than taking those lessons and applying them practically. Learning "how to reason" is more valuable than getting to the right answer. I wish more professors -- and, heck, teachers in elementary/high school as well -- coach their students that way. :flowerforyou:0 -
I like the different approach to reasoning you brought to the discussion (and returning the thread to its original purpose :blushing: ). Also support this viewpoint because learning the textbook is a lot different than taking those lessons and applying them practically. Learning "how to reason" is more valuable than getting to the right answer. I wish more professors -- and, heck, teachers in elementary/high school as well -- coach their students that way. :flowerforyou:
Thanks! I appreciate your appreciation! :happy: :blushing:0
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