I just tried on some of my summer capri pants and none of them fit over my butt, and if they did I'm certain they won't button. *Sigh* But those aren't the significant figures I wanted to discuss today.
I'm just going to do as my adviser suggest but I wanted to see what everyone's opinion was on significant figures.
I'm going to run through some thought experiments. Hope they make sense.
I measure a sample and get the value 10 with an error of 10%. This is 10 (+/-) 1. Significant figures all well and good. Then I measure another sample and get 5 with the same error. This is 5 +/- 0.5. But with sig figs it's 5.3 +/- 0.5. All good and agreeable.
Now say I want to put these two numbers in a table
10 +/- 1
5.3 +/- 0.5
I hate this. I want all my numbers to have the same amount of numbers after the decimal. Am I just being neurotic or does anyone else have this need for constancy?
Next, I analyze 25 samples and the average value is 10 but the standard deviation (or standard error) is 0.3 but the error of each analysis is 10%. I wouldn't want to round my standard deviation, so shouldn't my average value be allowed one more decimal place? My adviser says no but my organized self says YES I want all my numbers to have the same amount of decimal places.
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3 comments:
They may not need the same number of decimal places, but it would be nice if the had the same number of sig figs. For instance, 10 +/-1 and 5.3 +/- 0.5 both have two sig figs, which is OK in my book.
Imagine you are working with something that grows exponentially. Would the tenth decimal place of the last data point (say, 17892383.4) be as meaningful as that of the first data point (5.3)?
Something else I learned in error analysis: your error determines the number of sig figs in your final data value. If you have an error of 123, then round the error to its largest sig fig - 100. So your data point should be rounded to the 100s place as well. So for an error of 0.5123 and data value of 1.5478, the reported value is 1.5+/-0.5 .
I had to do alot of this magic in looking for trends in my trendless data. It also helps to do a Q-test to throw out lousy data. http://en.wikipedia.org/wiki/Q_test
Hi Jenni, I googled a topic and your blog came up. A post you had from April:
"I’m afraid of never finishing my dissertation.
I’m afraid of not getting a job
I’m afraid that once I get a job I will be no good at it."
Can I just say, I feel the exact same way. Not that it's great to feel like this, it's nice to know that someone else understands the feeling. Most times when I express my fears such as these, my family or friends say, "What are you talking about, you are educated, smart, just finished your Masters, etc.", but that doesn't make the fear go away. Why is it that sometimes those of us with so much passion for education get scared by a little thing called a "job"? For me I know that alot of it is that I feel like I am going to get trapped into a routine (job) that I am unhappy with and I feel like if that happens there might not be any way out. Crazy right? But I guess that's why fear is so powerful. It has the ability to convince us that the illogical is logical, that the unreal is real, that feelings of fear will manifest, and so on. You may have read this b/f but just in case you haven't, here is something I wrote down that someone gave me along time ago. Perfect timing for me to come across something like this:
OUR GREATEST FEAR~Marianne Williamson
Our greatest fear is not that we are inadequate,
but that we are powerful beyond measure.
It is our light, not our darkness, that frightens us.
We ask ourselves, Who am I to be brilliant,
gorgeous, handsome, talented and fabulous?
Actually, who are you not to be?
You are a child of God.
Your playing small does not serve the world.
There is nothing enlightened about shrinking
so that other people won't feel insecure around you.
We were born to make manifest the glory of God within us.
It is not just in some; it is in everyone.
And, as we let our own light shine, we consciously give
other people permission to do the same.
As we are liberated from our fear,
our presence automatically liberates others.
Take care,
Just getting back to blogging.
My blog: www.ReadWriteandLive.blogspot.com
well i'm not sure about the exact work you're doing, but i always want my numbers to have the same number of decimal points in my figures, and will write 4.00.
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