Designing Investigations
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(1 of 2)
Author: JA

Dear Dr. Harlen,

I am still working on how to provide appropriate materials and the right amount of structure to allow students to devise their own experiments and tests. We are first working on looking at data after an experience and putting the pieces together. Any suggestions you have about student experimental design and seeking more effective ways to test ideas would be most appreciated.


(2 of 2)
Author: Wynne Harlen

Dear JA --
I think it’s useful to think in terms of different kinds of investigations. The dictionary definition of ‘investigate’ is to ‘observe, study or closely examine’. All the practical work involving first hand study of materials would therefore be called investigation (or inquiry, since this is defined in terms of investigation).

There are different kinds of investigation, however, which emphasize different process skills and are appropriate for investigating different kinds of questions. The main types are:

  • information-seeking -- investigations carried out to see what happens, either as a natural process unfolds or when some action is taken, e.g., seeing eggs hatch, raising butterflies or silk worms, observing the expansion of water on freezing, seeing what things dissolve in water. They emphasise observation and communication skills. They are relevant at all stages but particularly for younger children.
  • comparing or fair testing -- investigation that often begin from a ‘which is best?’ question. Which detergent washes the clothes best? Which fertilizer is best for the plants? Which paper towel is best for mopping up water? The first step in these investigations is to turn the question into an investigable one by specifying the meaning of ‘best’ in a way that identifies the basis of comparison. So ‘which type of sugar dissolves best?’ has to be turned into, for example, ‘which type of sugar dissolves most quickly?’ These are popular and useful investigations since they involve children in identifying and controlling variables (amount of sugar, amount of water, temperature of water, presence or absence of stirring, etc). They also have the appeal of yielding information about real things from the actions carried out by the children. However it’s necessary to avoid a routine or formulaic approach, when the value for thinking becomes diminished.
  • pattern-finding -- investigations that apply where there is a relationship to be found between variables, e.g., the note produced by blowing across the top of a bottle with different amounts of water in it; the direction of a shadow cast by the sun and the time of day; the number of turns given to a wind-up toy and how far it will go. These investigations involve the same skills as ‘comparing’ investigations since the effect of changes in one variable have to be tested fairly, with other variables or conditions kept the same, but there is the added emphasis on interpreting data.
  • hypothesis-generating -- investigations which seek explanations to things such as: the appearance of dew on grass overnight; the misting of windows in certain conditions; the echo of foot-steps in some places; the behaviour of a ‘Cartesian diver’. The explanations are often in terms of the conditions or events that are associated with these observations rather than general scientific principles. The investigations begin with open-ended exploration of the phenomenon leading to the generation of a range of possible explanations. These can be checked against the evidence so far available by using the hypotheses to make predictions.
  • how-to-do-it investigations -- investigations where the end product may be an artefact or a construction that meets particular requirements – a model bridge that will support a certain load, for example.

As you can see, each has a particular emphasis and relevance to certain types of problem or question. In each case it’s important to enable children to plan the investigation and not to by-pass this by giving them instructions to follow. They will only use and develop the skills by doing the thinking for themselves. There must, therefore, be opportunities for children to start from a question and work out how to answer it, or to make a prediction and to think out and carry out their own procedures for testing it. Motivation to answer a question arises from 'ownership of it, so students must be involved in raising questions for themselves.

To take these steps by themselves is asking a great deal of young children and of older ones unused to devising investigations and they will need help which subsequently can gradually be withdrawn. Young children's experience should include simple problems such that they can easily respond to 'how will you do this?' For example, 'how can you find out if the light from the torch will shine through this fabric, this piece of plastic, this jar of water, this coat sleeve?' Often young children will respond by showing rather than describing what to do.

With greater experience and ability to 'think through actions' before doing them they can be encouraged to think ahead more and more, which is one of the values of children devising their own investigations. Involving children in this is part of setting an expectation that they will think through what they are going to do as far as possible.

For older children, help in devising and planning can begin, paradoxically, from reviewing an investigation which has been completed (whether or not the children planned it themselves), helping them to go through what was done and identifying the structure of the activity through questions such as

  • what were they trying to find out?
  • what things did they compare ( identifying the independent variable)?
  • how did they make sure that it was fair ( identifying the variables which should be kept the same)?
  • how did they find the result (identifying the dependent variable).
  • how did they use the result to answer the initial question?

When devising a new investigation the lessons learned from reviewing a previous one can be recalled, where perhaps variables were not controlled or initial observations taken when they should have been.

The teacher's role in this development can be summarised as:

  • refraining from giving instructions which prevent children thinking for themselves
  • providing time and a structure for planning
  • expecting children to think through what they do even it they do not write formal plans on paper for every investigation
  • reviewing plans in the light of what was done.

Thanks for your questions.



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