2. Here are the IB Physics student requirements for dealing with uncertainties:  Describe and give examples of random and systematic errors. Dealing With Uncertainties  Distinguish between precision and accuracy.  Explain how to reduce the effect of random error.  State uncertainties as absolute, fractional and percentage.  Determine uncertainties in calculations.  Show uncertainties as error bars in graphs.  Determine uncertainties in slopes and intercepts. Laboratory peer pressure

3. Uncertainties in calculations If the uncertainty in A is  A and the uncertainty in B is  B, then... (A   A) + (B   B) = (A + B)  (  A +  B) (A   A) - (B   B) = (A - B)  (  A +  B) Uncertainties in Sums and Differences (A   A)  (B   B) = (A  B)  (  A% +  B%) A   A B   B = ABAB  (  A% +  B%)  A%   100% AAAA  B%   100% BBBB Uncertainties in Products and Quotients Note: (A   A) n = A n  n  A% Uncertainties in Powers A   A = A  n  A% n n Uncertainties in Roots Question: Why do we have to use percent uncertainties for products and quotients?

4. Uncertainties in slopes STEP 1: Find the slope of the best-fit line m best. m best STEP 2: Draw in the error bars for the FIRST and LAST data points. STEP 3: Find the maximum slope m max allowed by your error bars. m max STEP 4: Find the minimum slope m min allowed by your error bars. m min STEP 5: Then the slope of our best fit is given by m best   m = m best  m max - m min 2 Uncertainty in Slope