I'm looking at Error analysis and still stumped.

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Soontir C'boath
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I'm looking at Error analysis and still stumped.

Post by Soontir C'boath »

At the beginning of the year, my physics class' first PDF was about Error analysis that we had to read about. To this day, I still have no clue what the heck to do with this thing. I reread this thing and I do it but it doesn't seem right at all.

Such as this lab I had this tuesday, I am doing the standard deviation of this lab as according to the equations and it looks sooo wrong. I got something to the tune of .24 +/- .11

Then my next problem is how to do the error bars on a graph. It said something in accordance to place the delta x and y on the plotted points which then confuses me as it shows that it's all over.

I am just dumbstrucked by this.
What I have been looking at is this. Warning: It's a PDF

Until then, I'm just going to write some of the lab report that doesn't need the graph.
I have almost reached the regrettable conclusion that the Negro's great stumbling block in his stride toward freedom is not the White Citizen's Counciler or the Ku Klux Klanner, but the white moderate, who is more devoted to "order" than to justice; who constantly says: "I agree with you in the goal you seek, but I cannot agree with your methods of direct action"; who paternalistically believes he can set the timetable for another man's freedom; who lives by a mythical concept of time and who constantly advises the Negro to wait for a "more convenient season."
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Kuroneko
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Post by Kuroneko »

Assuming you calculated .24±0.11 correctly, the error bar would run from 0.13 to 0.35. It sounds as if the lab would require you to do so for both the x and y direction (obviously, each would have their own error terms), effectively making a little cross (or a rectangle). If both x and y have a significant error term, this is a natural thing to do. I'm not very clear as to the nature of your difficulty.
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Ariphaos
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Post by Ariphaos »

Well the error bar for any given point he took would be + or - .11, so if it was .4 (say) he'd draw a bar along y from .29 to .51 at that point on the x axis, and it seems like this is what he's doing but his numbers are all over the map when he tries to draw a best fit line?

Perhaps you could run through the math you did and it'd be easier to see if you made a mistake calculating the standard deviation.
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Soontir C'boath
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Post by Soontir C'boath »

I felt it was so huge to have an error that far.

Thank you, both.
I have almost reached the regrettable conclusion that the Negro's great stumbling block in his stride toward freedom is not the White Citizen's Counciler or the Ku Klux Klanner, but the white moderate, who is more devoted to "order" than to justice; who constantly says: "I agree with you in the goal you seek, but I cannot agree with your methods of direct action"; who paternalistically believes he can set the timetable for another man's freedom; who lives by a mythical concept of time and who constantly advises the Negro to wait for a "more convenient season."
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