General Physics 1 - Accuracy and Precision PDF

GENERAL PHYSICS 1 WITH MS. VANESSA COLONA DESPE Welcome to class! Today's Agenda ATTENDANCE CHECKER PLEASE CHECK THE ATTENDANCE TRIVIA OF THE DAY CHECKING OF ASSIGNMENT CAN YOU GIVE ME THE EXACT MEASURE OF THOSE THINGS USING THE RULER PROVIDED 1. Coins 2....

GENERAL PHYSICS 1 WITH MS. VANESSA COLONA DESPE Welcome to class! Today's Agenda ATTENDANCE CHECKER PLEASE CHECK THE ATTENDANCE TRIVIA OF THE DAY CHECKING OF ASSIGNMENT CAN YOU GIVE ME THE EXACT MEASURE OF THOSE THINGS USING THE RULER PROVIDED 1. Coins 2. Nail 3. Sharpener Why we need to measure things accurately?  PRECISION AND ACCURACY How can we tell that our measurement is PRECISE? When do we tell that our measurement is ACCURATE? When do we tell that our measurement our RELIABLE?  You always have to make sure that you have reliable measurements. One way to do this is by repeating the measurement several times.  A reliable measurement will give the same results under the same conditions. The measurement is then precise or it has high precision. Thus, a set of measurements is precise when it is consistent. This means that the values are close too each another. Another way of testing the reliability of a measurement is by comparing it with a standard value. If the set of measurements is close to the true or accepted value, it is said to have high accuracy. The game of darts is good analogy for knowing the difference between precision and accuracy. Throwing three darts at the dartboard could produce a number of different patterns. A. The darts are close together (high precision), but they are far from the bull’s eye (low accuracy). B. The dark is closer to the bull’s eye (higher accuracy), but they are far from each other (lower precision). C. Shows the darts are close to each other and to bull’s eye (high precision and high accuracy).  You can numerically describe the consisted (precision) of measurements using VARIANCE. This measures how far or close the measurements are from the mean(average). Variance(σ2) is defined as the average of the squared difference of the measurements (x) from the mean The formula to find variance is: When N is the number of measurements done. The square root of the variance is called the standard deviation (σ). A standard deviation close to zero (0) indicates that the data points are close to the mean. High standard deviation indicates that the measurements are spread out over a wide range of values. When N is the number of measurements done. The square root of the variance is called the standard deviation (σ). HOW TO COMPUTE FOR STANDARD DEVIATION AND VARIANCE First, compute the mean or average of the measurements Then make a table for the calculation of deviations 2 (x- ) and square of deviations (x- ) for each measurement. Take note of the consistency of units. HOW TO COMPUTE FOR STANDARD DEVIATION AND VARIANCE To find the variance, you first have to get the mean of 2 (x- ) Get the variance. Next, get the standard deviation by getting the square root of the variance. TRY THIS! Example 1: Five of your classmates measured the diagonal length of the blackboard. Classmate A measured it as 2.24m Classmate B measured it as 2.46m Classmate C measured it as 2.65m Classmate D measured it as 2.55m Classmate E measured it as 2.39m Find the variance and standard deviation of the measurements. Also, express the average measurement in a form that includes uncertainty. EASY STEPS 1. ARRANGE YOUR DATA 2. COMPUTE YOUR MEAN 3. COMPUTE FOR DEVIATION 4. COMPUTE FOR SQ. OF DEVIATION 5. COMPUTE THE SUM OF SQ. OF DEVIATION 6. COMPUTE FOR THE VARIANCE 7. COMPUTE FOR THE STANDARD DEVIATION TRY THIS UNGROUP DATA 12,16,20,15,17,1 4,18,10,9,5 And we're done for the day! Keep safe! and Keep updated!