calculating the % margin of error - sample data survey data question

[thara vardhan-2]

Dear members

Sorry  I forgot to include a  sample of my data file. My data file has the
following variable columns


LAC             Freqlac    No satis   No dissat    No neutral  No don't
know   Total count   % sat     % dissatisfy    % neutral   % don?t know
Strawberry   83       26.93             7.44                 6 .76 3.29    
       44.41         60.63            16.74        15.22            7.41

reagrds
thara

I would be really thankful if any member could help me solve this problem
of calculating % margin of error.
 
From a survey conducted by an independent organisation for a question on
satisfaction with services provided by us:

I have a 4 scale response as 1) dis-satisfied 2) Satisfied 3) Neither 9)
Don?t Know

Using the aggregate function in SPSS I have calculated the number of
counts and percentage for each of the above.

I also have the frequency of responses by each Local command area as a
variable in my data file.

At 95% confidence level with an additional factor of 1.25 I have to
calculate the margin of error.

My colleague has given me the following syntax to calculate the percentage
margin of error in excel file

v5 =CONCATENATE(ROUND(100*1.25*1.96*SQRT((U5*(1-U5)/T5)),1),"%")

Where u5 is the percentage satisfied with services and t5 is the total
sample size for each LAC (obtained as sum of frequencies).

Lower limit u5-v5

Upper limit u5+v5

I tried to do the same in SPSS by using the two variables percentsatisfy
and freqlac in my SPSS file with syntax as:

COMPUTE Margine=(100*1.25*1.96*
SQRT(percentsatisfy*1-percentsatisfy))/freqlac.
EXECUTE.

The syntax as such, seems to be working but I get 0 values in the variable
column.

Thanks
Regards
thara



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[Hal 9000]

what does "Strawberry" mean?

On 6/20/07, Thara Vardhan <[hidden email]> wrote:

>
> Dear members
>
> Sorry  I forgot to include a  sample of my data file. My data file has the
> following variable columns
>
>
> LAC             Freqlac    No satis   No dissat    No neutral  No don't
> know   Total count   % sat     % dissatisfy    % neutral   % don?t know
> Strawberry   83       26.93             7.44                 6 .76 3.29
>       44.41         60.63            16.74        15.22            7.41
>
> reagrds
> thara
>
> I would be really thankful if any member could help me solve this problem
> of calculating % margin of error.
>
> From a survey conducted by an independent organisation for a question on
> satisfaction with services provided by us:
>
> I have a 4 scale response as 1) dis-satisfied 2) Satisfied 3) Neither 9)
> Don?t Know
>
> Using the aggregate function in SPSS I have calculated the number of
> counts and percentage for each of the above.
>
> I also have the frequency of responses by each Local command area as a
> variable in my data file.
>
> At 95% confidence level with an additional factor of 1.25 I have to
> calculate the margin of error.
>
> My colleague has given me the following syntax to calculate the percentage
> margin of error in excel file
>
> v5 =CONCATENATE(ROUND(100*1.25*1.96*SQRT((U5*(1-U5)/T5)),1),"%")
>
> Where u5 is the percentage satisfied with services and t5 is the total
> sample size for each LAC (obtained as sum of frequencies).
>
> Lower limit u5-v5
>
> Upper limit u5+v5
>
> I tried to do the same in SPSS by using the two variables percentsatisfy
> and freqlac in my SPSS file with syntax as:
>
> COMPUTE Margine=(100*1.25*1.96*
> SQRT(percentsatisfy*1-percentsatisfy))/freqlac.
> EXECUTE.
>
> The syntax as such, seems to be working but I get 0 values in the variable
> column.
>
> Thanks
> Regards
> thara
>
>
>
> This message and any attachment is confidential and may
> be privileged or otherwise protected from disclosure. If you
> have received it by mistake, please let us know by reply
> and then delete it from your system; you should not copy
> the message or disclose its contents to anyone.
>

[Marta Garcia-Granero]

Hi

I see a very simple error in your formula (a missing pair of parenthesis)
>> I tried to do the same in SPSS by using the two variables percentsatisfy
>> and freqlac in my SPSS file with syntax as:
>>
>> COMPUTE Margine=(100*1.25*1.96*
>> SQRT(percentsatisfy*1-percentsatisfy))/freqlac.
>> EXECUTE.
Try this one:

COMPUTE
Margine=(100*1.25*1.96*SQRT(percentsatisfy*(1-percentsatisfy)))/freqlac.

Notice the extra parentheses wrapping "1-percentsstisfy". Another
question: are percentsatisfy values really percentages (ranging from 0
to 100%? If so, then your formula should be
...SQRT(percentsatisfy*(100-percentsatisfy)....

>> The syntax as such, seems to be working but I get 0 values in the
>> variable
>> column.
It is quite logical that it happened so, since your formula computes the
square root of a quantity, multiplied by 1, and then minus itself!

HTH,
Marta Garcia-Granero

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