How Do You Calculate Standard Deviation and Error Probability for a Voltmeter?

[OEstudent]

1. A voltmeter is used to measure a known voltage of 100V. Forty percent of the readings are within 0.5V of true value. How do I figure out the standard deviation of the voltmeter, and how do I figure out the probability of an error of 0.75V?



2. I am trying to figure this problem out, however I do not know what to do with the 40% of the readings. Is that my n? Is n=40? And is the mean (99.5+99.6+99.7+99.8+99.9+100+100.1+100.2+100.3+100.4+100.5)/40? I am doing circles trying to figure this out.



Thanks for any input and help, OEstudent

 

[rock.freak667]

You have a 40% CI of 100V ± 0.5 V

Most likely your readings are normally distributed. So you need to get the Z_α value and use the formula for the CI.