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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. • When an experiment is performed, it is necessary to properly collect data so that a correct conclusion can be determined.
Aspects of Proper Data Collection • Things to be considered in collecting data: • Using the proper SI units • Example: centimeters, not inches • Recording units with each measurement • Always include a UNIT!!! • Using the appropriate instrument • Example: graduated cylinder, not beaker
Aspects of Proper Data Collection (continued) • Accurately reading the instrument • Example: knowing what each line on a metric ruler represents • Writing 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
Accuracy & Precision • 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.
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 • Types of trends • Positive correlation (direct, exponential) • Negative correlation (inverse, indirect or exponential)
Positive Correlation • When the dependent variable increases as the independent variable increases • If the variables increase at the same rate, it is a direct relationship
Negative Correlation • When the dependent variable decreases as the independent variable increases (this example shows an indirect relationship)
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: • As the “independent variable” increases/decreases the “dependent variable” increases/decreases. (choose one) (choose one)
Practice • (independent variable) (circle one) • (dependent variable) (circle one) As the _____________ increases/decreases the _____________ increases/decreases. WRITE YOUR OWN TREND STATEMENT
Practice Based on your two trend statements, do you see a connection between the amount of rainfall and the number of Mosquito incidents?
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 • Look at the common/frequent direction of the graph • Try to fit a line that will go in between the points… • And assess from there