Do we need to add a lot of detail when we talk about the controlled variables and why we’re controlling them?
Kia ora Jitse,
For AS91168, control variables are important at Merit and Excellence level. For Merit you should clearly identify which variables have been controlled, and where relevant state the value they have been maintained at. For example, “the distance travelled down the ramp was a control variable, and was maintained at 1.2m throughout the experiment”.
For excellence you need to justify why the variable had to be controlled, I would recommend linking this to your data or graph. For example: “If a longer ramp had been used at any stage during the investigation, then the time values would have been greater for those data sets. So even when a steeper angle was used, the time to travel down the ramp value would not have decreased proportionally, as shown in my graph.”
There is a lot more I would write for the example above, but I hope that answers your question. You might find this video helpful.