Probability and conclusions

[Jeff Wren]

Hi Dancing,

Based on the original wording of your example:

When I wear jeans, most of the time I tie my hair.

it would be possible that you always tie your hair when you wear jeans. That is because the word "most" does include the possibility of all (100%) in formal logic terms, which is a bit different than the way people commonly use the word "most" in everyday life.

You're right that the word "some" is less precise than "most," which in turn is less precise than "all." "Some" simply means "at least one" (or more precisely "anything but zero/none"). However, when solving logical reasoning problems involving formal logic, you can only be as precise as what you are given and what you can infer based on what you are given, so sometimes the answers need to be that level of precision. For example, if the only inference that you can make in a question is that "Some As are Bs," that would be what you'd be looking for in the answer (if it were a Must Be True question) and answers such as "Most As are Bs" would be incorrect.

As for whether to use conditional arrows or formal logic (such as a "most" diagram) when you encounter these types of statements, it really depends on the specific details of the logical reasoning question that you are solving. While there is nothing wrong with thinking about these ideas conceptually/abstractly, what is probably more helpful for the LSAT is to look at how these appear in actual LR questions and how to solve those questions on a case-by-case basis.

For example, one question that involves this concept first appeared as question 14 on LR 2 of Preptest 50 (September 2006 LSAT). (You can now find this question in Preptest 130.)

You can find the explanation for this question here:

viewtopic.php?f=549&t=11442

In that question, it would be beneficial to focus on the conditional reasoning (and diagram it conditionally) because the argument basically uses the contrapositive in the reasoning.

[Dancingbambarina]

Hi Dancing,

Based on the original wording of your example:

When I wear jeans, most of the time I tie my hair.

it would be possible that you always tie your hair when you wear jeans. That is because the word "most" does include the possibility of all (100%) in formal logic terms, which is a bit different than the way people commonly use the word "most" in everyday life.

You're right that the word "some" is less precise than "most," which in turn is less precise than "all." "Some" simply means "at least one" (or more precisely "anything but zero/none"). However, when solving logical reasoning problems involving formal logic, you can only be as precise as what you are given and what you can infer based on what you are given, so sometimes the answers need to be that level of precision. For example, if the only inference that you can make in a question is that "Some As are Bs," that would be what you'd be looking for in the answer (if it were a Must Be True question) and answers such as "Most As are Bs" would be incorrect.

As for whether to use conditional arrows or formal logic (such as a "most" diagram) when you encounter these types of statements, it really depends on the specific details of the logical reasoning question that you are solving. While there is nothing wrong with thinking about these ideas conceptually/abstractly, what is probably more helpful for the LSAT is to look at how these appear in actual LR questions and how to solve those questions on a case-by-case basis.

For example, one question that involves this concept first appeared as question 14 on LR 2 of Preptest 50 (September 2006 LSAT). (You can now find this question in Preptest 130.)

You can find the explanation for this question here:

viewtopic.php?f=549&t=11442

In that question, it would be beneficial to focus on the conditional reasoning (and diagram it conditionally) because the argument basically uses the contrapositive in the reasoning.

Thank you so much again. I am struggling with this segment from Dave's post:

Statement: Wear Jeans --> Tie hair 51%-100% (most) of time

Contrapositive: //////////Tie hair 51%-100% (most) of time --> ////////////////Wear Jeans
This is the same as: Tie hair 0%-50% (not most) of time --> ////////////Wear Jeans

Please note the dashes denote negated term



So, the issue I'm having is that with the most train, you can go backwards on the some train I.E. you can deduce that it's 1%-100% going backwards. Yet, in the contrapositive above, it's limited to only 0-50% once contraposited.

These are 2 different inferences and both revolve around "some", but one is more inclusive of possibility than the other.

Please help me understand what I'm missing.

Thank you so much