1. Data Collection, Accuracy, & Precision

2. Data Collection There is no such thing as a perfect measurement. Each measurement contains a degree of uncertainty due to the limits of instruments and the people using them. There is no such thing as a perfect measurement. Each measurement contains a degree of uncertainty due to the limits of instruments and the people using them. When an experiment is performed, it is necessary to properly collect data so that a correct conclusion can be determined. When an experiment is performed, it is necessary to properly collect data so that a correct conclusion can be determined.

3. Aspects of Proper Data Collection Things to be considered in collecting data: Things to be considered in collecting data: Using the proper SI unitsUsing the proper SI units Example: centimeters, not inches Example: centimeters, not inches Recording units with each measurementRecording units with each measurement Always include a UNIT!!! Always include a UNIT!!! Using the appropriate instrumentUsing the appropriate instrument Example: graduated cylinder, not beaker Example: graduated cylinder, not beaker

4. Accurately reading the instrumentAccurately reading the instrument Example: knowing what each line on a metric ruler represents Example: knowing what each line on a metric ruler represents Writing down the known digits of the measurement plus the estimated digitWriting down the known digits of the measurement plus the estimated digit Example: making a length measurement, and estimating the last digit as either 0 or 5 Example: making a length measurement, and estimating the last digit as either 0 or 5 Aspects of Proper Data Collection ( continued )

5. Accuracy & Precision Accuracy is how close a measurement, or experimental value, is to an accepted value, or standard. Accuracy is how close a measurement, or experimental value, is to an accepted value, or standard. Precision is how close a set of measurements are to one another. Precision is how close a set of measurements are to one another.

6. Seeing Accuracy & Precision

7. Determining Trends in Data

8. Trends When analyzing a graph, the ways that the data sets (dependent variable and independent variable) relate to one another are called trends When analyzing a graph, the ways that the data sets (dependent variable and independent variable) relate to one another are called trends Trends can also be seen as “patterns” in your data Trends can also be seen as “patterns” in your data Types of trends Types of trends Positive correlation (direct, exponential)Positive correlation (direct, exponential) Negative correlation (inverse, indirect or exponential)Negative correlation (inverse, indirect or exponential)

9. Positive Correlation When the dependent variable increases as the independent variable increases When the dependent variable increases as the independent variable increases If the variables increase at the same rate, it is a direct relationship If the variables increase at the same rate, it is a direct relationship

10. Negative Correlation When the dependent variable decreases as the independent variable increases (this example shows an indirect relationship) When the dependent variable decreases as the independent variable increases (this example shows an indirect relationship)

11. Stating the Trend Instead of simply saying if a trend is positive or negative, we can put the trend into a sentence using the format below: Instead of simply saying if a trend is positive or negative, we can put the trend into a sentence using the format below: As the “independent variable” increases/decreases the “dependent variable” increases/decreases.As the “independent variable” increases/decreases the “dependent variable” increases/decreases. (choose one)

12. Practice As the _____________ increases/decreases the _____________ increases/decreases. (circle one) (dependent variable) (independent variable) (circle one) WRITE YOUR OWN TREND STATEMENT

13. Practice Based on your two trend statements, do you see a connection between the amount of rainfall and the number of Mosquito incidents?

14. What if there isn’t a distinct trend? If you find that a trend is not clear with your graph, you should assess it based on where the pattern lies If you find that a trend is not clear with your graph, you should assess it based on where the pattern lies Look at the common/frequent direction of the graph Look at the common/frequent direction of the graph Try to fit a line that will go in between the points…Try to fit a line that will go in between the points… And assess from there And assess from there