Neal raised a number of interesting points regarding my use of skill checks in a previous post dated July 25, 2013, and I thought best to address it here.
One of the most fundamental questions raised is why use percentile dice in increments of five when I can use a d20 in increments of one? Well, the reason being is that it offers greater variety of possible outcomes to use a Percentile Die over a D20, but another reason is that percentile dice are used for skill checks (as in Runequest (RQ)- you must roll within the skill level to make the skill check and you must roll above it, to improve it). In MIDlands D&D, as in RQ, skills improve through successful usage, Abilities do not. It is NOT QUITE realistic that abilities remain stationary, but to be fair, adventure time keeps people from exercising and their abilities generally slowly deteriorate. So it is probably better that the character abilities stay chiseled in stone. By the same token, strongly believe that Gygax was wrong, when he wrote that even a Wish spell could not permanently raise one's ability score(!), each casing of the Wish spell will raise the ability by 1/10 of 1 ability point. That is the prime example of the King Gygax being foolish.
In my example of Brent the Paratrooper, read here: http://midlandstales.blogspot.com/2013/07/a-better-way-to-do-skill-checks.html
I change Brent's Parachute Jumping Skill from a percentile based 43% to a d20 ability-like 8, you always round down! This was done when Brent tried teaching Jumping to buddy of his. We use the ability modifier, and for this I like Moldway's symmetrical universal ability modifier table from the ability checks and multiply it by 5 to use with the percentile dice throws typically used in skill checks. When teaching the skill to his buddy, Brent would suffer a 5% penalty since his own skill is not that strong.
How did I come up with this? Ability Checks are very useful for mediating complex social dynamics that may occur between player characters and NPC's. Complex things, whose dynamics still challenge modern social science can best be mediated through a system of ability checks: thingslike teaching, carrying a conversation, negotiating, seducing, questioning and being questioned, falling in love, selling a used car. If facts and knowledge is involved, you do an INT check, if it is maturity and life experience that is needed to judge a situation, then it is a WIS check, when emotional issues are involved - trust, manipulation, empathy, assurance, social dominance, social graces, then it is a CHA check. If anybody wants to know the various ways of doing the ability check, just mention it I your comments and I will post on that. A complex social interaction between two participants should ALWAYS be role played and be mediated by a number of ability checks. A young magic user trying to become an apprentice to a great wizard, may try a variety of approaches as s/he role plays, and everything they do can be mediated/modified with an ability check. Attempts to seduce/impress will require CHA check, context of wits, INT, WIS ill be required to see through the game and ultimately it will be CHA when the magic user asks to be accepted. When teaching, the old Wizard will have to use CHA to establish trust and rapport with his apprentice, WIS to establish clear communication, and INT and his skills converted to the Ability scale to actually teach. Each roll will create modifiers that will express the teacher/apprentice relationship and will affect how much (if at all) the teacher will be helpful in learning a skill. When rolling to beat the skill, the student adds the teacher's success as a bonus to his percentile roll. Of course, there is role-playing and time spent, sometimes weeks and months, behind each roll.