Science seen as a practical problem solving exercise led to the focus on the science processes in the assessment framework. The category system represents the description of component skills which pupils need to solve problems. Performing investigations is the activity represented as a whole and is a synthesis of the other categories.

An example of a performance investigation question used in the 1981 survey at ages 13 and 15 was "Survival" The question is set in a context outside the school laboratory. The content includes such items as tin cans, measuring cylinders and thermometers, which allow, even encourage, the pupils to model the everyday context into a science one.

Performing investigations is primarily concerned with the different pathways taken by pupils between their perception of the problem and the solution at which they arrive. The pathway taken depends upon both the problem posed and the individual pupil's knowledge and skills, as demonstrated in the examples below.

For one pupil- Mark- the problem in "Survival" was to find out which of two materials got "hotter." To solve it, he cut out two jacket shapes, one from each material. He started the clock and subjected each jacket to hot air from the hair dryer for five minutes. He then felt each jacket and decided that the blanket was warmer.

For another pupil- Ann- the problem was to find out which material was the better insulator. She determined the rate of cooling when the two materials were placed around cans of hot water. In doing this she placed equal areas of material around identically sized cans. The aspects of performance illustrated by these examples are summarized in Table 3.

Problem formulation-

For both pupils, the first step is the generation of a problem.

Reformulation-  deciding what to measure

The next step is to choose the strategy to follow in order to solve the problem.

Mark Hold the material in the hand and measure heat.

Ann Wrap the material round cans of hot water and measure the rate of cooling.

Planning- setting up conditions

Once the experiment has been operationalized into an experimental set-up, further decisions have to be taken about the design.

Mark How much material? Is the hairdryer to be used?

Ann What temperature of water and how much? Which can(s)?

Using apparatus and making measurements

When this stage is completed the pupils must carry out their experiment.

Mark Is the stop-clock to be used to time? Should the temperature change be judged qualitatively?

Ann Should a beaker or a measuring cylinder be used to measure the volume of the water? How many thermometer readings are necessary?

Recording, interpreting and drawing conclusions

These operations lead to the collection and recording of data. These data have then to be interpreted so that conclusions can be drawn.

Mark and Ann have answered different questions--they have perceived the problem as being linked to thermal capacity and thermal conductivity respectively. Nevertheless each of them has gone through a number of identifiable stages as outlined in diagrammatic form in Figure 2.

For some pupils progress through the problem-solving chain is apparently linear. This may not necessarily be the case, however; they may have made a mental plan, evaluated it and amended it before putting it into practice. If they consider that their conclusion is a suitable solution to the perceived problem, their experiment is complete. However, for other pupils the process of evaluation may lead them to reject their conclusions and to take further action. They re-enter the chain and modify their experiment.

The kinds of actions that pupil evaluation can lead to are demonstrated in Figure 3 by reference to "Survival" and to Mark's and Ann's experiments.