chapter 3: experimental error Flashcards
what is experimental error
difference between the “true” value and the measured value
what are the 3 types of experimental error
systematic, random, gross(blunders0
what is systematic error/ determinate error
arises from a flaw in equipment or experiment design
what are ways to detect systematic error
- analyze a known sample
- use different method to ensure same quantity
- different labs analyze identical samples
- analyze blank sample
what are ways to correct systematic error
- calubriate glassware and instruments
- use standard addition
what is random error
arises from uncontrolled variables in measurement
- always present can’t be eliminated
- can be reduced through a better technique
what are some examples of random error
- reading a scale varies with invidual
- electrical noise in an instrument
what is a gross error(blunder)
due to accidental but significant departures from the procedure
- should be recorded in the lab notebook
- serious that data can be rejected or experiment is redone
what causes gross errror
procedural, instrumental, clerical mistakes
what are some examples of blunders
- calculation errors
- overshooting a titration end point
- dropping or contaminating sample
- instrument failure
what is the formula for absolute uncertainty and what is it
- expresses the margin of uncertainty associated with any measurement
- written as +- value
- example: buret reading of 12.35 +-0.02 means the true value could be in the range of 12.33mL to 12.37mL
what is relative uncertainty
compares the size of the absolute uncertainty with the size of its associated measurement
what is the equation for relative uncertainty
absolute/ magnitude of measurement
0.02mL/12.35mL
what is the equation for percent relative uncertainty
absolute uncertainty/ magnitude of the measurement x100
addition and subtraction of absolute uncertainty of the individual terms
efinal = square root ( e1^2+ e2^2+e3^2)
