# Help with error calculations.

1. Nov 10, 2006

### blackcat

for my coursework I'm meant to do error calculations.

say i measured a distance between two things five times and got these results:

0.104
0.104
0.104
0.108
0.108

now i've got to use this distance for my calculations. would you recommend i use an average (mean)? i suppose that's a stupid question.

my teacher also says: "You would get an estimate of random error by repeating results enough times to get a standard deviation for the random error.
"

so does this mean, for my example listed above, that i would say the error is (+-) value of s.d?

2. Nov 10, 2006

### OlderDan

The standard devition is often used as an indication of the uncertainty of the measurement. You would use the average of your measurements. If the errrors are truly random, the values of a large number of measurements would be normally distributed and about 68% of the measurements would be within 1 s.d of the average.

http://www.has.vcu.edu/psy/psy101/forsyth/normal.gif [Broken]

Last edited by a moderator: May 2, 2017
3. Nov 10, 2006

### blackcat

ok.

1) i'm sorry if this sounds stupid, but say i measure a weight on a balance that measures up to 2 dp. do i say the error is (+-)0.005.

4. Nov 10, 2006

### Hootenanny

Staff Emeritus
That's what I would do

5. Nov 10, 2006

### blackcat

THANK YOU!

Also thanks for your help on my other thread, I got it.

6. Nov 10, 2006

### Hootenanny

Staff Emeritus
My Pleasure