Strategy 1: Variable Y vs Variable X (lifted from question) X is independent and Y is dependant keeping z constant.
Diagram: Schematic box like diagram only . Do not copy diagram again. ....
Strategy 2 : What and how to measure the variables X.(instrument and method used)
Strategy 3: What and how to measure the variable Y. (instrument and method used)
Strategy 4: Repeat steps ....by varying X to obtain 6 sets of readings of X and Y .
Strategy 5. Plot a graph of lg Y vs lg X . If the graph is linear.... valid ... n = gradient and intercept =....
Reliability: Repeat the measurement of Y to obtain the average reading of Y
Some other constant of variables to be mentioned here .