which do you prefer dimensional analysis or ration & porportion

carolinapooh, BSN, RN · Mar 13, 2006

IMO - dimensional analysis leaves less room for error. You can see all of your work and you are able to make sure everything that cancels out does indeed cancel out.

Ratio confuses me.

Trauma Columnist · Mar 13, 2006

Okay guys - help an old (and mathematically deficient) nurse out - what the heck is dimensional analysis???

I use ratio and proportion myself and always check my calculations with a calculator and another RN.

minnielynn · Mar 13, 2006

Okay guys - help an old (and mathematically deficient) nurse out - what the heck is dimensional analysis???
I use ratio and proportion myself and always check my calculations with a calculator and another RN.

3.75 TBLS=_________CC

Dimensional Analysis Method

Answer Units = cc

Conversion Factor = 15 cc : 1 TBLS

3.75 TBLS X 15cc/ 1TBLS = 15cc

so TBLS & TBLS cancel out leaving only cc

3.75 (X) 15 (/) 1 = 56.25 (rounded to 56cc)

I hope this is understandable. I don't use this method so I really don't get it myself, but I am willing to learn it if it's more commonly used with less room for error.

Fun2, BSN, RN · Mar 13, 2006

The words "Dimensional Analysis" sounded scary before learning it in my Chemistry class.

IMHO, it has proven to be the simplest way of converting when there are several things that need to be converted before getting to the final answer.

DON'T KNOW WHAT IT IS? CHECK OUT THIS SITE:http://www.chemistrycoach.com/use.htm

Daytonite, BSN, RN · Mar 13, 2006

Okay guys - help an old (and mathematically deficient) nurse out - what the heck is dimensional analysis???

It is a method of setting up an equation of fractions with labels on them that you are going to multiply together. It is most often used in chemistry when trying to find how many moles of a this or that you need to get a particular reaction going. The significant feature of DA is that you set up all the fractions of an equation so that the labels in the numerators cancel out the labels in the denominators until you are left with the label you want on the final answer. The numbers always work out. Some of the fractions will be conversion factors where the numerator and denominator must equal the same thing, such as 12 inches/1 foot or 1 minute/60 seconds. For IV problems the drip factors of tubings are included in these equations as, for example, 15gtts/1ml for standard tubing.

Actually, I always use the old dose desired over dose on hand times amount on hand formula at work because it works so well for everything. I'll help the students set up DA problems here on the forums.

llg, PhD, RN · Mar 13, 2006

I have spent many years teaching new grad orientees -- some of whom use ratios and some of whom do dimensional analysis. The ones who use ratios almost always adjust to real world easier than those who use dimensional analysis (DA).

DA works fine in school and on tests where the questions are formatted to conform to DA. However, in the real world, the "questions" come in the form of situations witch sometimes require multiple steps. I have seen to many "DA people" freeze up when they can't figure out what to put in their single equation because they can't see the whole big complex picture at one time.

The "ratio people" rarely freeze up like that because they aren't trying to incorporate the complex, mulitple steps into one equation. They start out with the first ratio ... then move on the next ... etc. working towards a solution until they arrive at one ... step by step ... one piece at a time.

DA would work in those big, complex situations, but most new grads can't grasp all the steps at one time to form that 1 big equation. They need to break it down into steps and they aren't used to doing that -- so they freeze.

llg

minnielynn · Mar 14, 2006

I have spent many years teaching new grad orientees -- some of whom use ratios and some of whom do dimensional analysis. The ones who use ratios almost always adjust to real world easier than those who use dimensional analysis (DA).
DA works fine in school and on tests where the questions are formatted to conform to DA. However, in the real world, the "questions" come in the form of situations witch sometimes require multiple steps. I have seen to many "DA people" freeze up when they can't figure out what to put in their single equation because they can't see the whole big complex picture at one time.
The "ratio people" rarely freeze up like that because they aren't trying to incorporate the complex, mulitple steps into one equation. They start out with the first ratio ... then move on the next ... etc. working towards a solution until they arrive at one ... step by step ... one piece at a time.
DA would work in those big, complex situations, but most new grads can't grasp all the steps at one time to form that 1 big equation. They need to break it down into steps and they aren't used to doing that -- so they freeze.
llg

So I can use R&P for any problem, incl drips, etc? I took a pharm class at a college I attended 3 semesters ago and I used DA. I did not like it, but that professor only taught us with the DA formula, back then I had not idea that there were other ways to work out the problems.