3. What is Data?
Information, in the form of facts or figures obtained from experiments or surveys, used as a basis for making calculations or drawing conclusions
Encarta dictionary

4. Two Types of Data:
Qualitative
Quantitative

5. Qualitative Data
Information that relates to characteristics or description (observable qualities)
Information is often grouped by descriptive category
Examples
Species of plant
Type of insect
Shades of color
Rank of flavor in taste testing
Remember: qualitative data can be “scored” and evaluated numerically

6. Qualitative data, manipulated numerically
Survey results, teens and need for environmental action.

7. Quantitative Data
Quantitative – measured using a naturally occurring numerical scale
Examples
Chemical concentration
Temperature
Length
Weight…etc.

8. Quantitative Data
Measurements are often displayed graphically

9. Quantitation = Measurement
In data collection for Biology, data must be measured carefully, using laboratory equipment
(ex. Timers, metersticks, pH meters, balances , pipettes, etc)
The limits of the equipment used add some uncertainty to the data collected. All equipment has a certain magnitude of uncertainty. For example, is a ruler that is mass-produced a good measure of 1 cm? 1mm? 0.1mm?
For quantitative testing, you must indicate the level of uncertainty of the tool that you are using for measurement!!

10. How to determine uncertainty?
Usually the instrument manufacturer will indicate this – read what is provided by the manufacturer.
Be sure that the number of significant digits in the data table/graph reflects the precision of the instrument used (for ex. If the manufacturer states that the accuracy of a balance is to 0.1g – and your average mass is 2.06g, be sure to round the average to 2.1g) Your data must be consistent with your measurement tool regarding significant figures.

11. Finding the limits
As a “rule-of-thumb”, if not specified, use +/- 1/2 of the smallest measurement unit (ex metric ruler is lined to 1mm,so the limit of uncertainty of the ruler is +/- 0.5 mm.)
If the room temperature is read as 25 degrees C, with a thermometer that is scored at 1 degree intervals – what is the range of possible temperatures for the room?
(ans.s +/- 0.5 degrees Celsius - if you read 15oC, it may in fact be 14.5 or 15.5 degrees)

13. Looking at data
How accurate is the data? (How close are the data to the “real” results?) This is also considered as BIAS
How precise is the data? (All test systems have some uncertainty, due to limits of measurement) Estimation of the limits of the experimental uncertainty is essential.
Let’s do a sample problem: