#17 - The tiny hummingbird weighs little, but its egg is

[Administrator]

Complete Question Explanation

Must Be True. The correct answer choice is (C)

This stimulus consists of information with no explicit conclusion, but the numbers presented indicate a
trend. It seems, at least anecdotally, that as the weight of a bird increases, the weight of its egg, relative
to the size of the bird, decreases. This trend will likely be relevant, since we are asked which proposition
is illustrated by the statements in the stimulus.
Answer choice (A): This choice might seem attractive, because the stimulus does discuss wide variation,
but no volume-to-weight ratios are addressed.

Answer choice (B): The stimulus supports the idea that the ratio of egg-weight to body-weight increases
as the bird gets smaller, but that does not mean the eggs themselves are larger in any absolute sense.

Answer choice (C): This is the correct answer choice, as it reflects a proposition illustrated by the
stimulus. As the size of the adult bird increases, the ratio of egg-weight to body-weight decreases.

Answer choice (D): The stimulus itself does not allow us to make conclusions about the absolute sizes of
the eggs, so we cannot make this comparison.

Answer choice (E): Since the stimulus never offered specific numbers to allow for comparison of bird
size, we cannot conclude from the stimulus whether bird size or egg size has greater variation.

[maximbasu]

Hi, I chose A and the correct answer is C.

I understand the rationale. I don't understand how you can make such a large generalization about all bird species while the stimulus only gives three random examples.

I actually think A is a better answer because it doesn't make such a large generalization about all bird species with no evidence whatsoever.

Please advise,
MB

[Clay Cooper]

Hi Maximbasu,

Thanks for your question.

I understand your frustration. I think the reason that A is wrong and C is correct is the specific wording of the question stem. We are not asked in this MBT question what we are asked in many MBT questions - essentially, which of the following can we prove based on the information above?

Instead, this questions asks us a slight variation: which of the following principles is best illustrated by the statements above? Remember, a principle is a rule. So, what we are asked is: which of the following rules do the examples of the birds above best illustrate?

I think, then, that C is better than A. Note that C could even turn out in this case to be untrue, and it would still be the answer choice best illustrated by the examples given in the stimulus. For example, even if the hummingbird, goose, and ostrich are outliers, and the rule given in C is not true of birds in general, it is still the rule best illustrated by the examples mentioned.

Does that help? I think it's always a good idea to be absolutely as literal as you can about what you are being asked in the question stem.

[Legallyconfused]

Hi everyone!

I am just really confused about the idea of ratios in this sense. I thought ratios were like 2:3 (two boys to every 3 girls in a classroom). We are only given the percent. How do we translate that to a ratio if I don't know the given weight of a hummingbird, goose, or ostrich?

Hummingbird weight: 0.12 oz
Goose weight: 11 lbs
Ostrich weight: 220 lbs

Hummingbird egg weight (15%): .018 oz
Goose egg weight (4%): .44 lbs
Ostrich egg weight (1.6%): 3.52 lbs


The ratio of egg weight to body weight is smaller for larger birds than for smaller ones. What does smaller mean in this sense? Does it means the egg weight is closer to the body weight for smaller birds than larger birds? As in the gap between the two weights is smaller?

Hummingbird ratio: .018 : 0.12
Ostrich ratio: 3.52 : 220

Any help would be amazing!
Thank you!

[Adam Tyson]

Ratios can be compared in the same way that fractions can be compared, Legallyconfused. A ratio of 1:3 is smaller than a ratio of 2:3, just as 1/3 is a smaller fraction than 2/3. The comparison is not about actual numbers, but about relative relationships. We don't need to know the exact weights of any of these birds or their eggs, we just need to know the relationships, which were provided to us. In this problem, since the figures are given in terms of percentages, it would be easiest to set up the ratios in terms of 100, because a percentage IS a ratio (the percentage is the figure compared to, or out of, 100).

Hummingbird egg weight is 15% of hummingbird adult weight: that is a ratio of 15:100 (think of that as "15 units of egg weight for every 100 units of adult bird weight)
Goose egg weighs 4% of adult weight: 4:100
Ostrich egg weighs 1.6% of adult weight: 1.6:100

As the birds get bigger, the ratios get smaller. That's answer C!