Salmonberry Plants

Salmonberry plants can be found all along the Pacific coast. Salmonberry plants are a food source for many animals in Pacific coast ecosystems including hummingbirds, deer, and bear. Scientists conducted a field study to learn about salmonberry plant populations in different habitats in Washington.

Field Study Question:How does the salmonberry plant population vary by habitat?

Procedure:

  1. Go to the salmonberry field study area. Record location, date, time, and temperature.
  2. Choose a random location in the forest edge habitat.
  3. Measure a 5-meter-by-5-meter plot and label as Plot 1.
  4. Count the number of salmonberry plants in Plot 1. Record as Plot 1 for the forest
    edge habitat.
  5. Repeat steps 2 through 4 for Plot 2 and Plot 3, choosing a new location in the forest edge habitat for each plot.
  6. Repeat steps 1 through 5 for the stream bank and forest habitats.
  7. Calculate and record the average number of salmonberry plants for each habitat.

Data Collected:

Location: Forest edge, stream bank, and forest habitats

Date and Time: May 1, from 11:00 a.m. to 2:00 p.m.

Temperature: 10° C to 15° C

a)Describe a step in the field study procedure that ensured the results of the field study would be reliable.

b)Describe a step in the field study procedure that ensured the results of the field study would be valid.

Task Title: Salmonberry Habitat
Item number: 1 Cognitive Complexity: 2 (page 1 of 2)
Performance Description
A 4-point response demonstrates the student understands the Content Standard INQC: Conclusions must be logical, based on evidence, and consistent with prior established knowledge.
Item Specification 1: Generate a logical conclusion that is supported by evidence from the investigation and/or provide a scientific reason to explain the trend in data given a description of and the results from a scientific investigation.
AND
Content Standard INQF: Science is a human endeavor that involves logical reasoning and creativity and entails the testing, revision, and occasional discarding of theories as new evidence comes to light.
Item Specification 1 and 2: 1. Evaluate an investigation in terms of validity (e.g., answered the investigative question with confidence; the manipulated variable caused the change in the responding variable). 2. Valuate an investigation in terms of reliability (e.g., reliability means that repeating an investigation gives similar results).
Item and example response / Points
INQF(2)
a) The response describes a step in the field study procedure that ensured the results of the field study would be reliable.
Examples:
  • They counted salmonberries in three plots instead of just one in each habitat type.
  • There were three plots for each habitat type.
Notes:
  1. Responses which describe controlling more variables are describing an improvement in validity rather than reliability and may not be credited.
  2. Responses which describe one way to change the field study procedure to improve the reliability of the field study may be credited one point (e.g., test 5 plots instead of 3, do the same investigation the next year).
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INQF(1)
b) The response describes a step in the field study procedure that ensured the results of the field study would be valid.
Examples:
  • All of the plots were counted on the same day.
  • They used 5 meter by 5 meter plots every time they counted.
  • There were three different types of habitats instead of just two.
Notes:
  1. Responses that describe doing the same field study again are describing an improvement in reliability rather than validity and may not be credited (e.g., repeat for 3 more days/months/years).
  2. Responses which describe one way to change the field study procedure to improve the validity of the field study may be credited one point (e.g., count in a fourth type of habitat, make sure the same person does all the counting).
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Teaching tips:

To help students distinguish validity from reliability, have students remember “r for repeat” (increasing trials) and “v for variables” (increasing the number of control variables).

Have students use what is already in the given experimental procedure rather than making up additional improvements.

Remind students on prompts while designing their experiments to include steps for validity and reliability.