PTC NSWHomeGEMSEvaluating
Evaluating

Role of mentors

In this step mentors come back for their third and final school visit. Mentors should be able to assist students with their conclusion (based on the collected data) and to evaluate the investigation – what worked, what didn't work, what would they do another time, how could the investigation be extended or progressed.

The point of a scientific investigation is not to prove a prediction or hypothesis. Data is data. What does the data show? An investigation is considered to be highly successful when it is a fair test, when there is replication and when the data is meticulously collected – it is not about 'getting the result that I thought I would'.

Read about interpolating and extrapolating data and when it is appropriate to make generalisations about results.

At this point students should be brought together as a class to share their findings. Read why re-visiting the original brainstorm mind map is so important for widening and connecting student learning.

Have students evaluate how well they worked in their groups with this exercise – How did we go? 

 

Further Reading

 Interpolating and extrapolating 

One major source of errors in student investigation is the lack of an adequate data set in terms of the range and number of samples of data. For example, if students are investigating the effect of salt in water on plant growth and they only choose to use fresh water or very salty water with which to water the plants then plants will either grow normally or not at all. There is no sensitivity in the data. A greater range of concentrations of salty water should be used to water different sets of plants.
Also, an investigation into water salinity and plant growth may not produce large differences in the height of plants with only slightly different salt concentrations. It is therefore most important that great care is taken with measuring the height of plants so that small differences can be identified.

 

 Making generalisations 

A key concept to teach students in data processing and concluding is that care is necessary when going beyond the specific results and conclusion of an investigation to discuss the more general implications. For example, it would be easy to make the generalisation that sea levels will rise as a result of the land ice melting and entering the ocean because of global warming as a result of a simple investigation measuring water levels as a large 'land based' ice block melts in a tub of water. Actual data suggests that a major cause of sea level rising as a result of global warming is thermal expansion of water. This is due to the behaviour of water as it warms above four degrees Celsius. The point is that in the real world many factors come into play that are not present in simple controlled experiments, and to make sweeping generalisations from such data is not a good idea.

 

 Re-visiting the theme around which the investigations were planned 

It is most important to return to the initial brainstorm/mind map of when the theme was linked with topics and to collate the conclusions made across the class. This completes the learning cycle and enables students to see how their results tie in with the class topic for example, energy.

Students need to understand the science underpinning the reason for their result so that they are able to clearly articulate the why of their findings. An example would be that an increase in temperature (increasing the amount of heat energy) causes solid ice to change to liquid water, which then runs into the ocean, thus raising the sea level. The amount of heat energy influences the rate of melting.

 

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