TWO TYPES OF DATA MEASUREMENT RULES PRECISION & ACCURACY ACCURACY FOR A GROUP OF DATA Measurement, Accuracy, & Precision

I. Two Types of Data A. Quantitative Data – this data is almost always numeric and is based on a well defined scale B. Qualitative Data – this data is descriptive in nature and typically uses words rather than numbers 1. Ex. Tracey has a medium build, is 1.49m tall, has been alive for 13yrs, and has blonde hair. 2. Ex. The solution bubbled for 3s, producing a blue foamy material and losing 0.15g of mass.

II. Measurement Activity A. Quickly draw the table below in your lab notebook Group 100 cm Marks 1o cm marks 1 cm marks

III. Rules for Measurement A. The last digit in a measurement is always an estimate 1. This means that when we are measuring, we keep writing numbers until we are forced to estimate a digit. 2. The estimated digit is the last number we write. B. You estimate one digit past the smallest increment (mark).

Comprehension Check What is the smallest increment and proper measurement for the picture below? Smallest Increment: Measurement: 10 mL57 mL1 mL 60.3 mL25.4 cm 0.1 cm8.12 cm10 cm100 cm1 cm 80 cm 23 cm

IV. Precision A. Precision tells you how close measurements are to one another 1. For example, you measure the mass of a beaker of water to be g and your partner then measures the same graduated cylinder with water to be g. Are your measurements precise? a. Yes the two measurements are very close to one another

Comprehension Check Three students measure the height of the same plant. There data is summarized in the table to the right? Were their measurements precise? After talking it over, they discovered that they were all measuring to different places on the plant. They decide as a group to always measure the height in the same way. Are their new data precise? Student Length (cm) Max15.3 Julia19.6 Thomas16.0 Student Max17.6 Julia17.4 Thomas17.5

Accuracy A. Accuracy refers to how close a measurement or group of measurements is to the actual value (how correct it is) 1. For example, Mike measures the length of a piece of notebook paper to be 15in long. Was Mike’s Measurement Accurate? Explain Your Answer a. Mike’s measurement is NOT accurate because the real length of notebook paper is 11in (8½ x 11).

Accuracy for a Group of Data If you measure the same value more than once, you must take the average of all the data points before determining whether the data is accurate  Four students measure the length of a piece of paper.  Are the individuals accurate?  Is the group accurate? Student Length (in) Mike9 Trisha13 John10 Tammy12 No one is accurate, because all the measurements are far from 11in. The group is accurate, because their average is 11in.

Comprehension Check

Are the darts accurate, precise, neither, or both?