Required Practical 12 - Sampling Flashcards

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1
Q

Explain why it is important to use a statistical test in analysing the results of an investigation

A
  • results may be due too chance
  • confirm difference is significant
  • in order to accept or reject null hypothesis
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2
Q

Describe how you would place quadrats at random

A
  • random number generator on calculator

- to determine coordinates to place quadrat in a gridded area

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3
Q

Describe how you would decide the number of quadrats to use in order to collect representative data

A
  • enough to carry out a statistical test
  • large enough to be reliable and collect in available time
  • calculate running mean
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4
Q

Explain why biologists collect data randomly

A
  • avoid bias
  • to collect representative data
  • so statistical tests can be calculated
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5
Q

Explain why it is important to check the repeatability of measurements

A
  • increases reliability of measurements

- differences less likely to be due to measurement error / anomalies

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6
Q

Describe how you could use a scatter diagram to check the repeatability of measurements made by two observers

A
  • plot one set of results against the other
  • expect to see points lying close to line
    OR
  • plot both sets against variable
  • look for overlapping/ corresponding points
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7
Q

Suggest precautions taken when carrying out sampling

A
  • allow sufficient time to elapse before taking further samples so vegetation can recover from trampling
  • study organisms in situ or take minimum number and return
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8
Q

Evaluate density in measuring abundance of a species

A
  • most accurate
  • time consuming
  • not suitable when there are too many individuals / individuals are difficult to identify
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9
Q

Evaluate percentage cover (% area of quadrat) in measuring abundance of a species

A
  • more accurate than frequency but less time consuming compared to density
  • subjective so unreliable
  • does not consider overlapping individuals
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10
Q

Evaluate frequency (% squares in quadrat) in measuring abundance of a species

A
  • quick, basic overview
  • inaccurate
  • does not consider overlapping individuals
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11
Q

Draw a conclusion using data provided

A

Give BALANCED Argument

  • correlation data shows
  • state if correlation is weak or strong
  • give anomalous examples
  • sample size small so unreliable
  • other factors not considered
  • cannot be sure since no statistical analysis
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12
Q

Suggest precautions taken when sampling

A
  • avoid trampling on vegetation
  • allow sufficient time to elapse before further studies
  • study organisms in situ / remove and return and minimum amount
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13
Q

State when to use quadrats and transects

A

Quadrats - uniform distribution

Transects - distribution changes over an area

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14
Q

Suggest why a certain number of samples is taken

A
  • too many would be too time-consuming

- too few would be unreliable and insufficient to eliminate anomalies

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