Do Now & Announcements Grab a Handout (for after the quiz) Turn in HW up front to be checked (make sure your name is on it!) Clear desks and prepare for quiz Unit 1 Test ~WED 2/3

Accuracy vs. Precision

Accuracy vs. Precision Accuracy=how close the results are to the correct answer (Bull’s eye!) To determine accuracy, we look at the average of our results. Precision= how often the same results are measured/obtained To determine precision, we look at the consistency of our results.

AVERAGE ACCURATE NO

each trial/measurement precise NO

Accuracy vs. Precision Practice YES YES

Accuracy vs. Precision Practice 4.67 NO 99 YES YES NO

Percent Error A quantitative way we can look at the accuracy of a set of data if the true value is known For this class, we’ll say the data is accurate if the percent error is less than 5%

The freezing point of water is 273. 2 K, but it was measured at 250 The freezing point of water is 273.2 K, but it was measured at 250.1 K. What is the percentage error? Calculate the top part first, then divide! 23.1 273.2 ×100% 250.1−273.2 273.2 ×100%= =0.084×100% =𝟖.𝟒% NOT ACCURATE

Percent Error Practice 2) 4.49 % 3) 888% 4) 3.88%

Measurement: When using tools with graduated “tick marks”, you should estimate one decimal place beyond the value of the smallest tick mark! 0.7 cm Each tick mark represents 1 cm  round to nearest 0.1 cm

Each tick mark represents 0.1 cm  round to nearest 0.01 cm

Reading Graduated Cylinders: Liquids form a curved surface when in graduated cylinders. As a standard, you should read the liquid level from the bottom of the meniscus