Data Collection, Accuracy,

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Data Collection, Accuracy, Precision
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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.

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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

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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

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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.

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Seeing Accuracy Precision
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Determining Trends in Data
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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)

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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

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Negative Correlation

• When the dependent variable decreases as the
  independent variable increases (this example
  shows an indirect relationship)

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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)
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Practice

• As the _____________ increases/decreases the
  _____________ increases/decreases.

WRITE YOUR OWN TREND STATEMENT
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Practice
Based on your two trend statements, do you see a
connection between the amount of rainfall and the
number of Mosquito incidents?
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What if there isnt 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