Hi!

About the coverage factors, can you please enlighten me a bit? I've just read about this on

NIST , the coverage factor is...

<i>

Coverage factor
In general, the value of the coverage factor k is chosen on the basis of the desired level of confidence to be associated with the interval defined by U = kuc. Typically, k is in the range 2 to 3. When the normal distribution applies and uc is a reliable estimate of the standard deviation of y, U = 2 uc (i.e., k = 2) defines an interval having a level of confidence of approximately 95 %, and U = 3 uc (i.e., k = 3) defines an interval having a level of confidence greater than 99 %. </i>

and they made an example of...

<i>The following are examples of uncertainty statements as would be used in publication or correspondence. In each case, the quantity whose value is being reported is assumed to be a nominal 100 g standard of mass ms.

Example 1

ms = 100.021 47 g with a combined standard uncertainty (i.e., estimated standard deviation) of uc = 0.35 mg. Since it can be assumed that the possible estimated values of the standard are approximately normally distributed with approximate standard deviation uc, the unknown value of the standard is believed to lie in the interval ms ± uc with a level of confidence of approximately 68 %. </i>

having said that, um, i would like to know where the 68% come from. and what exactly is a coverage factor? is this the equivalent of the coverage factor, like k=2=xx%

Plus, on an entirely different matter, I would like to know how we estimate the errors on leads used in electrical measurements.

Thanks in advance.

cheers!