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

Group100 cm Marks

1o cm marks

1 cmmarks

1

2

3

4

5

6

7

8

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 mL 57 mL1 mL 60.3 mL25.4 cm

0.1 cm

8.12 cm

10 cm100 cm1 cm 80 cm23 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 194.98g and your partner then measures the same graduated cylinder with water to be 194.96g. 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?

StudentStudent Length Length (cm)(cm)

MaxMax 15.315.3

JuliaJulia 19.619.6

ThomasThomas 16.016.0

StudentStudent Length Length (cm)(cm)

MaxMax 17.617.6

JuliaJulia 17.417.4

ThomasThomas 17.517.5

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?

StudentStudent Length (in)Length (in)

MikeMike 99

TrishaTrisha 1313

JohnJohn 1010

TammyTammy 1212

No one is accurate, becauseall the measurements are farfrom 11in.

The group is accurate, becausetheir average is 11in.

Comprehension Check

Comprehension Check

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