PERCENT ERROR-MEASURES ACCURACY

• RECORDED VALUE- The value that was measured

• ACCEPTED VALUE- The true value.• PERCENT ERROR- used to determined how

close the recorded value is to the accepted value.

PERCENT ERROR FORMULA:

ACCEPTED VALUE – RECORDED VALUE X100 ACCEPTED VALUE

A shopper measures a 5 pound bag of onions and finds that its 5.2 pounds. What is their percent error?

% Error = / 5.0 lbs – 5.2 lbs/ x 100 5.0 lbs

% error = /-0.2 lbs/ x100 5 lbs

% error = 0.04 x100 = 4%

PERCENT DEVIATION- HOW MUCH A MEASURED VALUE IS OFF FROM THE AVERAGE(no accepted value).

Mean- average value

Absolute deviation- the absolute difference between the mean and the recorded value.

% DEVIATION

AVERAGE ABSOLUTE DEVIATION X100 MEAN

%D = (Da/M )x100

STEP 1: Take several readings and find the average.

ex: You measure a length of a wooden block and get four measurements. Find your % deviation.

8.9cm + 9.1cm+ 9.0cm + 8.8cm= 35.8cm

Mean = 35.8/4 = 8.95

STEP 2: FIND ABSOLUTE DEVIATION FOR EACH VALUE

/ 8.9-8.95/ = .05cm

/ 9.1-8.95/ = .15cm

/9.0 – 8.95/= .05cm

/ 8.8-8.95/ = .15cm

STEP 3: FIND AVERAGE ABSOLUTE DEVIATION

.05 + .15 + .05 + .15 = .40cm

.40cm = .1cm 4

STEP 4: USE FORMULA

% DEVIATION=

AVERAGE ABSOLUTE DEVIATION X100 MEAN

% deviation= 0.1cm x100 = 1.1% 8.95cm

What does it all mean?