Accuracy vs Precision What should I be doing

Accuracy vs. Precision What should I be doing during the video? • Defining all important vocabulary words • Rewind and replay as you need • • Take careful notes • Write down questions to ask in class or mark places you do not understand well • Summarize what you have learned Do all example problems, diagrams, etc.

Hit the Bullseye!

A B C D Which of these dartboards has accurate results? Which of them has precise results?

Based on this labels…what do you think the SCIENTIFIC definition “accurate” vs. “precise” is?

Describing Quantitative Results ACCURATE PRECISE • How close the result is to the accepted answer or known value • How close a group of numbers are to each other • How “correct” a measurement is • How consistent or repetitive the measurements are

Accurate? Precise?

Accurate? Precise?

Example Problem A chemist is trying to determine the identity of blue powder at a crime scene by measuring its melting point. She predicts that the crystals are a sample of Methamphetamine. Back at the lab, she conducts 3 trials of a melting point test and gets the following measurements: 1 °C, 2 °C and 7 °C for the melting point of the solid. The actual melting point of crystal meth is 3 °C 1 2 7 10 Calculate the average = _________ + _____ = _______ ÷ 3 Were her measurements precise? Was her prediction accurate? Explain thoroughly. 3. 3 = _______

Let’s try this with actual data!

Let’s try this with actual data!

Analyzing Sources of Error When there is little error in a measurement, the result is accurate _____ When the same error occurs repeatedly, the result may be accurate. _______ precise but not _______ When random errors happens in a lab, the results will not be accurate precise or _____________. Suppose a graduated cylinder is not calibrated correctly.

10 9 8 7 6 5 9 / 16 Accuracy vs. Precision 4 3 2 1 Use your phone (or i. Pad) to log into the socrative app (room name is joevchem) and answer the question. When finished voting, in your notebook, defend your answer using data. Think of it like a CER where the answer you chose is your "C"laim. Your "E"vidence will be your data. And, your "R"easoning is an explanation of accuracy vs. precision. Jared is practicing for a golf tournament. He normally hits the ball 250 yards on his drives. He hits three balls with his driver for a distance of 190 yds, 195 yds, and 187 yds. Which of the following is true?