HOMEWORK #4  Experiments

(see Syllabus for due date and points possible)


Locate a news article that describes an experimental test of an abstract model (e.g. high fat diets cause cancer, increased biodiversity causes increased stability, "green-house" gases cause global warming, the "hole" in the ozone causes increased skin cancer, evolution occurs via natural selection). You will need to (i) relate how the goal, model, and experiment relate to each other, and (ii) identify the design features of the experiment.

Detailed instructions for the "ideal" homework assignment follow. The actual format is a writeable pdf that you download (HW4template.pdf).  See the homework guidelines, but especially note the following.

i)               Your grade on this assignment will depend on the suitability (e.g., depth) of the article you chose. Articles that don’t describe many design features won’t allow you to get a great score.

ii)             the article must be less than 9 months old and should not be from an on-line quiz.

iii)            upload the article along with your filled pdf template on your Canvas account for this class.



How to use the Experiments pdf template


Type your name in the pdf form field.


Type the title, source, and date of the article on the pdf. Upload the article (as a scan, if need be). We want to be sure we have access to the article, so a little redundancy does not hurt.


In one sentence or less, describe the goal of the study in your article.


Experiments are usually done to choose between 2 or more different models that pertain to the same goal.  (Typically, one model is as simple as "drug X improves cancer treatment" and the other "drug X does not improve cancer treatment"). Identify two alternative abstract models that the experiment addresses. If only one is mentioned in the article, propose the second one yourself. List them as

Model 1:

Model 2:


Here, as with some prior assignments, it is important that the models clearly address the goal.  And the experiment must address the goal as well.


1. Experiment. Remember that an experiment involves a manipulation and is not merely taking a measurement.  Some of the things being observed need to be changed in some way from the natural order. Explain why the study is an experiment. That is, what manipulation was done and for what purpose? (e.g., "subjects were chosen for the study, which involved giving each patient either drug X or a placebo to test the effect of drug A." Or, "each advertisement was placed in 100,000 magazine copies to evaluate which received more responses.")

2. Controls. (A)  What was a factor that was controlled for? If “none,” list a factor that was not controlled for (other than the treatment factor).

(B) What was the control group?

(C) What was the treatment group?

3. Ideal data. What features of ideal data were present in the experiment? Fill in the following information for each of the five design features of ideal data:

a. Relevant? Considering the goal and model you have identified, is this design feature relevant to the study? If so, answer the next two points as well.


b. Status: In one word state whether this particular design feature is present, absent or ambiguous/uncertain. Ambiguous (uncertain) means either that the article did not state explicitly that this particular design feature is present at any level or absent, or that it is not possible to infer from what is stated whether the feature is present or absent.  If the feature is present at any level, it counts as present.


c. Quotes: Quote the article directly.  Copy from the article the sentence or phrase that either describes the specific design feature, states that this design feature is not present, or indicates ambiguity. Do not include more than is necessary.

Follow this format for each of the 5 ideal data features.  You should have at least 3 of the 5 features present for full credit:

A. Explicit Protocol

1. Relevant?

2. Status:


B. Replication

1. Relevant?

2. Status:


C. Standards

1. Relevant?

2. Status:


D. Randomization

1. Relevant?

2. Status:


E. Blind

1. Relevant?

2. Status: (treat a placebo as evidence of blind)



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Copyright 1996, 1997 Craig M. Pease and James J. Bull. All rights reserved.