Uncertaintiy And Measuring Mistakes, Accuracy Flashcards
If they mention measuring something that gives a BIGGER VALUE and whynthat leads to more accuracy what to say?
Bigfer value hints at uncertiwnties
It’s likely that you’re using the same uncertainty but bevause you have a bigger number to mewsude over, then the percentage uncertainty decreases and it becomes more accurtse
When you have two pieces of equipment same that are used backed ti back (like meter rulers) what do you to find total uncertainty
Add the separate uncertainties together
So meter fuller = 1 mm + 1mm = 2mm
When there is an uncertainty in one thing and they say what percentage ERROR DOES THIS CAUSE IN ANSWER, what does it mean?
So why do we divide by 2 if sqaure root?
It just means PERCENTAGE UNCERTAINTY OVERALL
So remember how you add them up, if it’d squared muktilky by two
If it’s sqaure root, divide by 2!!
How to increase accuracy of oscilloscope measure amplitude
1) decreasing uncertainty
2) using means
IMPORTANT
1) turn time base off
2) turn y gain down so that the wave stretches higher to its maximum height ( same voltage , less gain so more squares).
- higher height means lower percentage uncertainty overall !
- count the squares peak to peaks , multiply by y gain, divide by 2!
2) 2nd idea is to increase / decrease time gain ti give different heights
- count squares peak to peak multiply by y gain , divide by 2
- do this for many different y gains and heights, count them together AND FIND AVERAGE FOR ACCURATE ANSWER
What does accuracy vs precision mean?
Accuracy means how close to is to the actual value
Precision refers to uncertainty!
How to find uncertainty in something like sin theta?
The uncertainty in sin theta is just = to the uncertainty in theta
- remember that any function does not CHANGE THE UNCERTAINTY OF A VALUE
- now you may have calculated sin theta but when dealing with theta always use lengths that have been DIRECTLY MEASURED
- therefore typically use tan function rather than calculating hypotenuse for sin
- know that theta = act tan (O/H) and thus uncertainty in theta uncertainty in O/H
Add these up, done !
Remember uncertainties in any measurement is the same as the uncertainty
Say you measured 10 wavelengths, uncertainty in one is the same as 10 so it’d less, don’t forget
Random vs systematic error
How to reduce random error
Random error is due to things can’t control, to reduce , take repeats
- more precise instruments
- use computers to avoid human error
This suggests that uncertainty in equipment is to do with random errors
2) systematic error is an error that will always be there as a result in a flaw in method or faulty equipment
- this error can easily be fixed, whereas random can’t
Uncertisnty in equipment, what kind of error is that
Random, can’t get close to the true value so don’t know what it is, taking it over repeats will probably be better
Might be confusing, just remember
Remember if they don’t give uncertainty like they did in that 6 marker, how can you estimate it ? Anyways so that you can back up your 6 marker
Can estimate it by taking the LAST value of the decimal as absolute uncertainty, give so,e number man
