[Blindmath] statistical formulas

Wed Oct 24 01:22:02 UTC 2012

Hi Kathy,
I'm sorry that you have had such a difficult time. Taking stats
period, and especially doing stats online, is very challenging for
many sighted students too, so please don't feel like your struggles
are an indication of your abilities. Such an un-accommodating person
really shouldn't be in the teaching business, in my opinion.
Best,
Arielle

On 10/23/12, Kathy Roskos <kroskos at cox.net> wrote:
> Arielle,
>
> I appreciate the advice.  Unfortunately, this particular instructor has no
> idea how to deal with a blind person, and would rather not do so if he could
>
> help it.  I did ask him to write out the formulas in words or simple
> symbols.  His solution was to go out and buy some sophisticated formula
> writing software, send them to me that way, which had no better results in
> me reading them, and then get angry with me because he bought the expensive
>
> software out of his own pocket and can't be reimbursed.  When I told him I
> was just asking him to write out the formulas more simply by hand, he said I
>
> didn't understand that these are not "canned formulas", and he couldn't do
> it that way.  Basically I have been fighting an uphill battle the entire
> course.  This correlation stuff is my last assignment, and I am just trying
>
> to get it done and get the heck away from this instructor.
>
>     Thanks for the advice anyway.  When it comes to math, I feel utterly
> stupid.  I am generally very good in school, but this course is trying hard
>
> to beat me.
>
> Kathy
> ----- Original Message -----
> From: "Arielle Silverman" <arielle71 at gmail.com>
> To: "Blind Math list for those interested in mathematics"
> <blindmath at nfbnet.org>
> Sent: Tuesday, October 23, 2012 7:49 PM
> Subject: Re: [Blindmath] statistical formulas
>
>
>> Ryan,
>> Is the covariance the same thing as the cross-product? The formula you
>> gave looks similar to the formula I learned for computing something
>> called the cross-product, which goes in the numerator of the
>> correlation formula. The denominator is the product of the variances
>> or sums of squares of X and Y.
>> I believe there are several different ways to compute correlation
>> coefficients by hand. I used to know how to do it but it's been five
>> years since I've learned it so I don't quite remember. Also your
>> instructor or textbook might favor one specific formula. In general,
>> what I would suggest is to email your instructor for the online course
>> and ask them to send you the formula in words or simple math symbols
>> as Ryan did. I have done this a few times and will likely do it again
>> since I am taking structural equation modeling with a textbook in
>> Daisy format. Screen readers and Daisy players cannot read Greek
>> letters and sometimes have trouble with equations in PDF format, but
>> they should be able to read an equation that is written in the body of
>> an email message or in a Word doc.
>> BTW, if you are allowed to use a computer to calculate Pearson's r, it
>> is very easy to do in Excel.
>> You might also try posting your question to the new NFBNet social sciences
>>
>> list:
>> www.nfbnet.org/mailman/listinfo/social-sciences-list_nfbnet.org
>> Best,
>> Arielle
>>
>> On 10/23/12, Ryan Thomas <rlt56 at nau.edu> wrote:
>>> Yes, it's the product of the deviation from the mean in each variable
>>> summed.  It looks like
>>>
>>> sum from i = 1 to n of (xi-xbar)*(yi-ybar) where xbar and ybar are the
>>> means.  I'm not sure what you mean by raw scores versus deviations.
>>> You can get around not computing the covariance by using some of the
>>> other identities which may avoid the deviations, but it's not very
>>> difficult if you use some computer application anyway.
>>>
>>> On 10/23/12, Kathy Roskos <kroskos at cox.net> wrote:
>>>> Thanks for the help.  I am really dense where math is concerned.  What
>>>> exactly do you mean by the covariance?  Do I use deviation scores and
>>>> figure
>>>>
>>>> the variances for both  X and Y and multiply them together?
>>>>
>>>> I have read  that you can use raw scores or deviation scores to figure
>>>> correlations.  Which method is easiest?
>>>>
>>>> Kathy
>>>> Please excuse my ignorance.  I have  ----- Original Message -----
>>>> From: "Ryan Thomas" <rlt56 at nau.edu>
>>>> To: "Blind Math list for those interested in mathematics"
>>>> <blindmath at nfbnet.org>
>>>> Sent: Tuesday, October 23, 2012 8:01 AM
>>>> Subject: Re: [Blindmath] statistical formulas
>>>>
>>>>
>>>>> For random variables X and Y, the correlation coefficient r is the
>>>>> covariance between x and y divided by the product of the variances of
>>>>> X and Y.  Depending on what statistics you're in there are other
>>>>> identities dealing with sum of squared regression and other terms.  I
>>>>> hope that's helpful though.
>>>>>
>>>>> On 10/23/12, Kathy Roskos <kroskos at cox.net> wrote:
>>>>>> I am new to this list.  I am taking a statistics class online and am
>>>>>> having
>>>>>> trouble getting jaws to read the formulas.  Does anyone out there
>>>>>> know
>>>>>> about
>>>>>> calculating r values for correlational data?
>>>>>>
>>>>>> any advice would be appreciated.
>>>>>>
>>>>>> Kathy
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>>>>>
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