Date: Thu, 13 Oct 2011 06:04:21

Author: B R Sitaram

Subject: Re: Excellent use of significant digits

Post:

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Even worse than this is when you find that "the *** bird is 8.9 cm long".
What has happened of course is that the length has been averaged at 3.5" and
then converted to cm! The fact that calculators are readily available makes
things worse: for example, while watching a cricket match, you may be told
that a batsman has a strike 42.9 runs per hundred balls faced; when you look
carefully, you realise that he has only faced 7 balls so far in his career
and has scored 3 runs from them!
Sitaram

On 13 October 2011 03:50, Jerry DiMarco wrote:

> Sorry, too many assumptions about significant digits. I'm with the
> failblogger...
>
>
> Jerry D
>
>
>
> At 10/12/2011 03:42 PM, you wrote:
>
>> Jerry,
>>
>> Total Calorie calculation:
>>
>> 10 +/- 1 Cal
>> 8 +/- 1 OZ
>> 20 +/- 1 OZ/Bottle
>>
>> 20 * ( 10 / 8) = 25 Cal/Bottle
>>
>> Propagating the errors for that gives 25 +/- 4 Cal per bottle. I'd call
>> that one significant digit. Round the 5 even (or truncate) and a bottle has
>> 20 Calories.
>>
>> You could claim that the 8 should really have an error of 0.5. But that
>> still gives you an error on the final answer of 3 Cal. 20 Calories is still
>> a perfectly reasonable way to write down that result.
>>
>> Paul
>>
>>
>> On Oct 12, 2011, at 2:20 PM, Jerry DiMarco wrote:
>>
>> > At 10/12/2011 01:59 PM, you wrote:
>> >> ......
>> >> This one has great potential for teaching about significant digits.
>> >>
>> >> http://failblog.files.**wordpress.com/2011/10/**
>> 6456cc3f-222f-45e7-a778-**56cc9f38923b.jpg
>> >> ......
>> >
>> > But not for basic math, as the calorie tally shows. Wonder how many
>> bottles went out before they discovered that mistake?
>> >
>> > Jerry D
>> >
>>
>
>
>


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Even worse than this is when you find that "the *** bird is 8.9 cm lon=
g". What has happened of course is that the length has been averaged a=
t 3.5" and then converted to cm! The fact that calculators are readily=
available makes things worse: for example, while watching a cricket match,=
you may be told that a batsman has a strike 42.9 runs per hundred balls fa=
ced; when you look carefully, you realise that he has only faced 7 balls so=
far in his career and has scored 3 runs from them!
SitaramOn 13 October 2011 03:50, Jerry D=
iMarco wrote:
=A0 =A0 Sorry, too many assumptions about significant digits. =A0I'm w=
ith the failblogger...

=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0Jerry D


At 10/12/2011 03:42 PM, you wrote:

Jerry,

Total Calorie calculation:

10 +/- 1 Cal
8 +/- 1 OZ
20 +/- 1 OZ/Bottle

20 * ( 10 / 8) =3D 25 Cal/Bottle

Propagating the errors for that gives =A025 +/- 4 Cal per bottle. =A0I'=
d call that one significant digit. =A0Round the 5 even (or truncate) and a =
bottle has 20 Calories.

You could claim that the 8 should really have an error of 0.5. =A0But that =
still gives you an error on the final answer of 3 Cal. =A020 Calories is st=
ill a perfectly reasonable way to write down that result.

Paul


On Oct 12, 2011, at 2:20 PM, Jerry DiMarco wrote:

> At 10/12/2011 01:59 PM, you wrote:
>> ......
>> This one has great potential for teaching about significant digits=
.
>>
>> http://failblog.files.<=
/u>wordpress.com/2011/10/6456cc3f-222f-45e7-a778-56cc9f38923b=
.jpg

>> ......
>
> =A0 =A0 But not for basic math, as the calorie tally shows. =A0Wonder =
how many bottles went out before they discovered that mistake?
>
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0Jerry D
>



-- Take a look=
at our website=
for more information about the exciting work we do and to download great s=
tuff! Click here t=
o see our toys and kits!


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