Hi, JBrown,
Thanks for the question!
Yes, your prephrase might have been part of the issue here. Let's do a quick diagram of this problem for our discussion:
- Decreasing percentage of Disease X treatment money spent on Standard Treatments.
- Increasing percentage of Disease X treatment money spent on Non-Standard Treatments.
- Standard Treatments are Effective.
- Non-Standard Treatments are not Effective.
We may assume that treatments are either Standard or Non-Standard.
Unknowns include:
- Total amount of money spent on Disease X treatments.
- Amount spent on Standard Treatments.
- Amount spent on Non-Standard Treatments.
The conclusion is:
- Less money is spent on Effective treatments.
This conclusion deals with one of our unknowns: "Amount spent on Standard Treatments."
We do not know the actual amount spent on Standard Treatments. However, we do know the percentage spent on these Standard Treatments has been decreasing.
Let's consider your prephrase:
"over the past decade there was an increase in spending on nonstandard treatment"
Even if we were to know that the amount spent on nonstandard treatments increased, we would still not know that the actual amount spent on Standard, Effective treatments decreased. It could be possible that both amounts increased, just with Non-Standard increasing more quickly, or with the amount spent on Standard Treatments remaining the same. Let me illustrate:
- Starting amounts: $50 for ST. $50 for NST.
New amounts: $50 for ST. $100 for NST.
Even though the NST amount has gone up, the ST amount has not gone down. However, the percentage spent on ST has declined from 50% to 33%, which agrees with the premises.
To justify the conclusion that the actual amount on ST went down, we need some additional information that we can add to the premises that guarantees that the conclusion is valid (this is the Justify Equation™).
Answer choice (E) does this. Let's illustrate:
- Starting amounts: $50 for ST. $50 for NST.
New TOTAL amount: $80.
If the new total amount went down from $100 to $80 and if the percentage spent on ST has also declined, then it is a mathematical certainty that the amount spent on ST has gone down. It must be less than $50.
Does this make sense? Great question.