1. Accuracy, Precision, Qualitative, and Quantitative
Types Of
Measurement
Accuracy, Precision, Qualitative, and Quantitative

2. Types of Measurement Quantitative- uses numbers to describe
Examples:
3.25 meters
62 lbs
32°C
Qualitative- uses description to describe
Extra large
Hot
Blue

3. Qualitative or Quantitative?
It is hot outside.
Yesterday I ran 3 miles.
It was 102° outside this afternoon.
The balloon was big and blue.
The paper felt soft on my skin.
I need 3.25mm of string for my project.
I am 3 foot 4 inches tall.
Wow you’re short!!
Quantitative
Quantitative
Qualitative
Qualitative
Quantitative
Quantitative
Qualitative

4. Scientists Prefer… Quantitative measurements Why do you think that is?
Easy to check
Easy to agree upon, no personal bias
The precision of the measurement device determines the reliability of the value.

5. How Reliable are the Measurements?
Scientists use two word to describe how reliable their measurements are
Accuracy- how close the measurement is to the actual value
Precision-
How close are your measurements to one another
or…
How well can the measurement be repeated

6. Differences
Accuracy can be true of an individual measurement or the average of several
Precision requires several measurements before anything can be said about it
Why is that?

7. Let’s use a golf analogy

8. Accurate? No
Precise?
Yes

9. Accurate?
Yes
Precise?
Yes

10. Precise? NO
Accurate? NO

11. Accurate?
Yes
Precise?
We cant say!

12. In Terms of Measurement
Three students measure the length of a room to be:
10.2 m
10.3 m
10.25 m
If the room is 15.7m
Were they precise?
Were they accurate?
YES NO

13. Who is More Precise? Which group has the most precise data? Group T
How did you decide on that group?
Subtract the lowest measurement from the highest measurement for each group.
The group with the smallest difference is most precise
Group T

14. Precision of Instrument
Precision of Data
vs.
Precision of Instrument
The word precision can also be used to describe how the measurement device (balance, ruler, etc.) being used determines how many decimal places are used when collecting data.

15. How Many Decimal Places Should I Record?
Record a digit for all marks shown on measurement device.
The last digit in you data will always be the estimated digit.
Using the ruler below we will measure the blue rectangle.
The correct length is 2.35 inches
The 2 is certain because there is a mark on the ruler
The 0.3 is certain because there is a mark on the ruler
The 0.05 is our estimated digit because there is no mark for it on the ruler and we must estimate between 0.3 and 0.4

16. How Many Decimal Places Should I Record?
How long is the red rectangle?
5.7 mm
The 5 is certain because there is a mark
The 0.7 must be estimated between the 5 and 6 mm mark.
It is a little more than half way so we estimated 0.7

17. Proportions
Direct Proportions – Dividing one by the other gives a constant value
As one value increases the other increases
As one value decreases the other decreases
They move the same
The graph of a direct proportion will be a straight line

18. Proportions
Inverse Proportions – Multiplying one by the other gives a constant value
As one value increases the other decreases
As one value decreases the other increases
They move opposite of one another
The graph of a direct proportion will be a curved line