Farm Investigation
Screen 11 – Microscope
Students are told that a microscope can make small things look big, and so George uses a microscope to look more closely at a hair from the garden. When George first looks through the microscope, the hair looks blurry.
Item 11A
In 11A, students are told that they can move the blue circle on the microscope slider to see the hair more clearly, and are asked to find the position on the slider that makes the hair as clear as possible. This simulates the procedure for focusing a microscope in the laboratory, and assesses students’ ability to select the correct setting. There are five possible positions on the slider, only one of which shows the hair clearly. Students choosing the correct position were awarded full credit (1 point).
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Maximum Score Points: 1
Content Domain: Life Science
Topic Area: Characteristics and Life Processes of Organisms
Cognitive Domain: Knowing
Science Practice: Generating Evidence
Results 11A
Exhibit 22 shows the percentages of students in each country that were able to focus the microscope. This was a very straightforward task, intended to introduce the students to the operation of the microscope, and was completed correctly by 61 percent of the students, on average internationally. Girls performed a little better than boys on this item, on average (63% vs. 59% correct).
Item 11B
To probe their deductive reasoning skills, in 11B students are asked if George can tell by looking only at one hair from the garden under the microscope whether the hair came from the cow or the goat. To be awarded credit (1 point), students had to indicate that George could not tell from one hair only, and describe the additional information needed or the method by which the additional information could be obtained. For example, “No—George needs to compare the hair he found to hairs from each of the animals and see which match.”
Click video to play
Maximum Score Points: 1
Content Domain: Life Science
Topic Area: Characteristics and Life Processes of Organisms
Cognitive Domain: Knowing
Science Practice: Generating Evidence
Results 11B
Exhibit 23 shows that students found this item to be very difficult, with only 13 percent of students on average internationally providing an acceptable explanation.