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Chapter 11: Problem 30

Two different underground pipe coatings for preventing corrosion are to be compared. The effect of a coating (as measured by maximum depth of corrosion penetration on a piece of pipe) may vary with depth, orientation, soil type, pipe composition, etc. Describe how an experiment that filters out the effects of these extraneous factors could be carried out.

Short Answer

Expert verified
An experiment could be structured where, for each type of pipe composition, multiple pipe samples are prepared in various soil types and kept at the same depth and orientation. Half of these samples are randomly coated with coating A and the others with coating B. All samples are then exposed to the same conditions conducive to corrosion. After a defined period, the maximum corrosion depth on each pipe is measured and the means are compared statistically. The coating yielding lower mean corrosion depth is more effective.

Step by step solution

01

Define the Variables

The first point is to clearly define the variables involved in the experiment. The primary interest is in the dependent variable - the maximum depth of corrosion penetration, which would yield insights into the effectiveness of the coatings. The independent variable is the type of coating used - coating A and coating B. Several extraneous (or nuisance) variables are also mentioned, including depth, orientation, soil type, and pipe composition, which potentially influence corrosion but are not the focus of this experiment.
02

Control Extraneous Variables

For carrying out a controlled experiment, the aim is to isolate the effects of the independent variable on the dependent variable, by controlling for all extraneous variables. This could be achieved via one of two methods: 1) holding these extraneous factors constant across all trials or 2) randomly assigning elements to different trial conditions so that all potential confounding factors are equally distributed.
03

Design the Experiment

Take multiple pieces of pipe that are same in composition. For each composition, prepare pipe samples for each soil type, each with the same depth and orientation. Apply coating A to half the samples and coating B to the other half in a random manner to ensure there are no systematic biases in the data collection. After the application of the coatings, subject all samples to the same corrosive conditions.
04

Conduct the Experiment and Collect Data

The next step is to conduct the experiment over a set period of time, which should be long enough to allow corrosion to occur. At the end of this period, measure the maximum depth of corrosion penetration on each pipe.
05

Analyze and Interpret the Results

Finally, compare the mean depth of corrosion for pipes with coating A to those with coating B. Statistical testing is needed to determine if any observed difference is statistically significant or simply due to chance. If there is a significant difference, the coating associated with a lower mean depth of corrosion would be deemed more effective in preventing corrosion.

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