In planning a new experiment, an engineer has identified seven critical factors.
ID: 3173912 • Letter: I
Question
In planning a new experiment, an engineer has identified seven critical factors. The objective is to improve the tear strength of a new material. Working closely with the design and process engineers and the plant operations people, the engineer is quite certain that these factors are: the line speed, the processing temperature, the pressure generated by the rollers, the type of fibers, the bonding resins, the moisture content of the fibers, and the humidity in the plant. The plant is quite large and is not air conditioned. It would be quite expensive to dry the fibers or to control their moisture content as they come in large bales and are stored on trucks or in a warehouse. What would you select as the control variables in this experiment? What would be your noise variables?Explanation / Answer
Here, the variable of interest is the tear strength of the material. We have seven variables (i) the line speed, (ii) the processing temperature, (iii) the pressure generated by the rollers, (iv) the types of fibres, (v) the bonding resins, (vi) the moisture content of the fibers, and (vii) the humidity of the plant.
Since the plant can't be air-conditioned, the factors (vi) and (vii) based on moisture and humidity can't be controlled. Since the fibers can't be dried, the variable (iv) of types of fibres can't be controlled either. The other four variables (i), (ii), (iii) and (v) can be used as control variables while (iv), (vi) and (vii) will be the noise variables.