EK Bio question 740

[superman3]

I've posted the passage here (It will only be available for a few days):
http://docupub.com/docs/940a6ffd-4dc8-4e40-ad7f-f17a53a5de67/EK1001 Bio #740.pdf

Based on the passage, which of the following statements would strongly weaken the validity for the results obtained from the 3 experiments?
A. Identical cancer cells were utilized to conduct experiments 1 and 3.
B. Allow the tumor burden to increase in Experiment 2.
C. AM-mouse and AM2-mouse were not of the same species.
D. cancer growth is unpredictable and the experiment lacked a control group.

I understand why C is correct, but I'm not sure I understand why D, would not also be correct. The answer in C is basically equivalent to lacking a control group. Does it have to do with the fact that D also has a clause that the cancer growth is unpredictable (which is irrelevant because in general cancer growth is unpredicatble)?.

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[Chrome19]

I've posted the passage here (It will only be available for a few days):
http://docupub.com/docs/940a6ffd-4dc8-4e40-ad7f-f17a53a5de67/EK1001 Bio #740.pdf

Based on the passage, which of the following statements would strongly weaken the validity for the results obtained from the 3 experiments?
A. Identical cancer cells were utilized to conduct experiments 1 and 3.
B. Allow the tumor burden to increase in Experiment 2.
C. AM-mouse and AM2-mouse were not of the same species.
D. cancer growth is unpredictable and the experiment lacked a control group.

I understand why C is correct, but I'm not sure I understand why D, would not also be correct. The answer in C is basically equivalent to lacking a control group. Does it have to do with the fact that D also has a clause that the cancer growth is unpredictable (which is irrelevant because in general cancer growth is unpredicatble)?.

First of all, the experiment is well-controlled. The primary goal of the experiment is test whether the body's immune system is able to inhibit growth of cancerous cells. The naive mouse is the control here. So there's a control making option D wrong.

And the predictability or unpredictability of cancer is irrelevant and would not affect the conclusion of the experiment.

 

[superman3]

I agree with you that the experiments are well controlled. However, I interpreted the answer choice to mean consider the case where experiment 3 lacked a control group. Was I supposed to know to interpret it the way you did, because the question stem stated "Based on the passage"

Many of the mistakes that I'm making seem to be mistakes of this nature....question stem or answer stem interpretation errors, where I am being tripped up by semantics. This is really frustrating. Content mistakes can be fixed, but Idk about my interpretation of semantics.

edit: Actually, though this might be trivial, I suppose the fact that answer choice D mentioned "experiment," which is vague....because there were 3 different experiments, might have been a tip-off.

 

[Chrome19]

Just read the questions carefully. For example in this case:

Based on the passage, which of the following statements would strongly weaken the validity for the results obtained from the 3 experiments?

So you are required to integrate all the arguments from each experiment.

Read questions CAREFULLY, and if you practice more while doing this it will come easier. I made many of this kind of mistakes as well, but I never got them all sufficiently under control since I prepped in a short time. I still did ok.

 

[superman3]

Yup, I agree-see edit. This test is silly. It is becoming increasingly clear to me how people who know the material can still perform poorly on the test, particularly, if they do not have these types of errors (question stem interpretation, answer stem interpretation), under control. Thanks for the help!

 

[Morsetlis]

Last answer choice was a distractor. "If everything's ****ed up" isn't the correct choice because everything is not ****ed up. You're asked to select the specific change that would invalidate the experiment: to find a second uncontrolled variable.