Following on from the previous blog I would like to focus on the Design criteria of internal assessment.
I often feel that students fail to appreciate scientific methodology as a process whereby once a conclusion is drawn from data collected, others revisit the experiment to test and verify the claims. Therefore it is essential that the experiment is written in such a way that it can be accurately repeated. I show the video below at the beginning of the year.
Students should understand the necessity to write up a lab with sufficient detail to allow others to repeat the experiment. This starts with the research question, written with detail, focus and reflecting biological principles starting with the scientific name of the organism used and the place where data was carried collected (if an ecological survey).
A clear, focussed research question will state both the dependent and independent variable.
Most commonly, there are two types of appropriate teacher prompts for research questions.
- Firstly, where neither the dependent nor independent variables are given but the system to be investigated is identified. An example of an open-ended teacher prompt would be “Investigate an aspect of a pond ecosystem”.
- The second type of prompt is where the dependent variable is given by the teacher and the student must select the independent variable as well as appreciate the controlled variables. An example here is when the teacher tells the student to investigate one factor that affects the rate of photosynthesis in an aquatic plant.
The variables should be explicitly stated and explanations be given for the control of variables. For those variables which cannot be controlled, such as in the case of field work, the variables need to be monitored. Its also important that the dependent variable stated be that which is measured and not that which is calculated.
e.g. diversity is not the dependent variable if a student is counting the number of organisms and number of species present in a locality.
When using data loggers, the link needs to be explicitly stated as to what is being measured. If a pressure sensor is being used to measure the increased production of oxygen, then that needs to be stated and not simply ‘pressure’.
As the rubric clearly states, it is quantitative data that must be collected and not that which is qualitative.
The method can be a modification of an existing protocol but should be extended in some way and all steps need to be included, perhaps in bullet point form. Though the past tense is desirable, its not compulsory, students are often writing in a second language.
The rule for sample size is a minimum of 5 measurements, though clearly the bigger the sample size the better.
For the sake of assessment, the students should design their investigations individually. However, it is possible that an initial brainstorming exercise would be useful to generate ideas that could then be further developed by individuals. It is also possible for students to work in groups on their proposed investigations after their individual designs have been assessed.
Next time I will focus on Data collection and processing