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Course: Digital SAT Reading and Writing > Unit 3
Lesson 1: Command of Evidence: TextualCommand of evidence: textual (scientific) — Worked example
Learn the best way to approach a scientific command of textual evidence question on your SAT. First, spot the claim you need to support. This often the "hypothesis" in scientific texts. Then, rephrase the claim in your own words, and look for the best evidence to back it up in the choices. Created by David Rheinstrom.
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- But the text excerpt never mentioned comparison to other lakes though(22 votes)
- Yes, that is correct, but we're looking for evidence that isn't given in the text that would support what the text claims. And by comparing it to other lakes in Alabama that are similar except for the runoff factor, we can confirm that runoff is probably what's causing the fluctuation in pH, since the otherwise similar lakes didn't have as much fluctuation. Does that make sense?
Hope this helps!(47 votes)
- Why does D not support the hypothesis? Isn't it also saying that an increase in runoff leads to fluctuations?(9 votes)
- D doesn't directly support the hypothesis because it's saying that both air pollution and runoff increased when the lake fluctuated. So with option d, we don't know whether the air pollution caused the fluctuation or whether the runoff caused the fluctuation because both increased during that time when the lake fluctuated.
Does that help?(55 votes)
- i dont't get it, why can't option d not work? it's very similar to A(10 votes)
- it says both air pollution and agricultural pollution increased during the period when PH fluctuated but that does not necessarily mean it was caused be the chemical runoff and could have been anything. Hence D is not specific nor does it directly support the hypothesis(12 votes)
- So all you have to do is process of elimination?(5 votes)
- that's seems so hard ahah, i thought it was d... anyway i guess i often can't indentify the right claim :(
But still i'm trying lol(6 votes)- i think it was A because it is really the only answer choice that mentions farmland. (that's how i look at it at least)(1 vote)
- Hey there, so option A says that other lakes fluctuate less because there aren't as much farmland runoff as Guntervislle lake meaning Guntersville Lake fluctuates more. What is the difference with option D there it said that because the farmland runoff increased, Guntervislle lake functuated?(4 votes)
- Identifying the option more direct is one of the major tasks(2 votes)
- Why is A the answer when there was no evidence in the text of comparing the two lakes I find that really hard to make sense.(4 votes)
- for me, honestly, this type of question feels the hardest.(4 votes)
- if a claim comes up on the SAT like we have to make a claim about an article what do we do if the article doesn't make sense to us do we guess or re read the article?(4 votes)
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Video transcript
- [Instructor] Hey, test takers. Let's take a look at this question from the reading and writing test. The pH level of lake
water, which indicates how acidic or basic the
water is, can be influenced by a variety of factors,
including acid rain, rock and mineral erosion,
and air pollution. Researchers in Alabama hypothesized that recent fluctuations
in the pH of the water in Guntersville Lake are
attributable to another source. Agricultural chemicals
that have been entering the lake through runoff. Which finding, if true,
would most directly support the researcher's hypothesis? If you'd like to give
this one a try on your own before I teach you some
specific strategies for this question type, please feel free to pause the video now. Okay, this is a science flavored command of evidence question. And these questions introduce some sort of argument or claim. Your job is to identify that argument and find the evidence that
most strongly supports it. For science passages, you won't need to lean on anything
you've studied previously. Everything we need to know
is contained right here in the passage. We want to figure out what the hypothesis is,
what the argument is, and support it. Follow me to the strategy
corner, won't you please? The question will introduce
a central claim or argument and it'll be stated very clearly so you won't have to go digging for it, but that's your first job. Identify the claim. Once you do that, create a test phrase that restates the claim in your own words. Doing this will give
you control of the idea and allow you to see it
restated differently. Once you've got your own
words version of the claim test it against the choices. Whichever choice matches your test phrase will be the answer. Let's reacquaint ourselves with what the question wants us to do. Okay, so which finding if
true would most directly support the researcher's hypothesis? Well, okay, look here
at the second sentence. Researchers in Alabama
hypothesized, there it is. That recent fluctuations
in the pH of the water in Guntersville Lake are
attributable to another source, agricultural chemicals that
have been entering the lake through runoff, right? There it is. That's our hypothesis. pH fluctuations were caused by runoff. So let me state that another way. Our test phrase here will be
runoff leads to pH change. And instead of the word change,
I'm just gonna use a delta. Let's test that against the choices. Okay, so which finding
would most directly support our hypothesis that runoff
accounts for the change in pH? Choice A, the pH levels
of otherwise similar lakes in Alabama that do not
receive as much runoff from farmland as Guntersville
Lake does fluctuated less than the pH of Guntersville
Lake did in the same period. Hey, how about that? This matches my test. We're talking about fluctuation, right? The degree of change. And this matches my
prediction or very nearly less farm runoff in similar lakes led to less fluctuation in pH. And we need to compare
apples to apples here. We need to compare Guntersville
Lake to other similar lakes so we can properly understand the impact of agricultural runoff. This has to be the answer on test A, I would circle it and move on. But let's knock out the other three just to say we did to
prove why A is the answer. So let's keep going. Choice B, the pH levels
of other lakes in Alabama that are near Guntersville
Lake tended to be lower than that of Guntersville Lake regardless of the degree
of fluctuation in the pH of Guntersville Lake. This doesn't support the hypothesis. The argument is not
about how low the pH is, it's about how much the pH
changes the fluctuation. Choice C, the amount
of agricultural runoff entering Guntersville
Lake steadily decreased during the period in which the
lake's pH level fluctuated, while a composition of that runoff remained largely unchanged. Again, this doesn't
support the hypothesis. It's not comparing
Guntersville to other lakes, and it talks about the
decreasing rate of runoff which isn't really
relevant to the hypothesis. Choice D, both air pollution
and agricultural runoff in the vicinity of Guntersville Lake increased during the
period in which the pH of Guntersville Lake fluctuated. If these polluting inputs both increased and the pH level in the lake fluctuated, then this would actually
weaken the hypothesis and that's not what we want. So goodbye choice D. See, once you've got that test phrase that support for the hypothesis, you can just rock it through the choices. Let's talk through a couple of top tips for questions like these. Top tip number one, be specific. You are looking for an answer choice that supports the claim
in the question stem. Nothing more, nothing less. So any choices that introduce
a new idea can be eliminated. We don't need evidence for anything else. Top tip number two, be strict. Anything that feels like it's
almost evidence for the claim is going to be too weak to be the answer. The answer needs to be all
right, not just partly right. Good luck out there test takers. You've got this.