Happy Homemaker, Ph.D.

A novice homemaker's attempts to use her engineering Ph.D. to serve her family

The Oatmeal Scotchie Experiment – The Technical Side

Disclaimer:  A couple of close friends have told me that sometimes my posts are such that they don’t understand them.  One friend who said this said she understood that I was “venting.”  I thought this was a great description, not venting as in complaining, but in needing an outlet to speak “my language” of applied stats, optimization, operations management, and process improvement.   I’m still trying to determine what audience I most want to reach with my stories, so for now, I write a little bit of everything.  So, if you’re one that I lose when I pull out my fun-for-me technical vocab, this post may not be for you.  Don’t worry.  Just skip it and tune in next time.  🙂

Designing an experiment properly is not an easy task.  I didn’t do a proper job of it when I explored my questions about the cookies this week, but I wanted to discuss some of the considerations a “real” experiment of this type would need to address.

First, what is the response variable?  In this case, I was looking at cookie quality, but how could that be measured?  I could have had multiple testers (Les, thanks for volunteering!) who would rate the cookies on a scale.  (Not my top choice as a non-continuous output variable, though.)  Since I was interested in voids, I could have taken samples and counted holes per square inch or per cookie somehow (if “holes” was well-defined to be consistently judged).  Since I have some idea of what the cookie should look like, I may have measured height (to gauge a flat or mounded cookie with calipers or something).  See, it’s getting a bit tricky already (or at least time-consuming), isn’t it?

Next, what factors did I want to explore?  Since the different amounts of flour and oatmeal were part of the recipe, I first wanted to look at a mixture experiment, but that wasn’t a good fit for this.  (Ooo!  Perhaps I can do a mixture experiment to optimize homemade play dough or something later…)  So, using the flour/oatmeal combinations given and regarding them as simply 2 choices seems best.  I didn’t think there was much to be gained by trying the in-between combinations.  Next, butter vs. shortening was of interest.  Also, I wondered about the pans, thinking there may be a butter-pan interaction.   Perhaps the refrigeration of the dough before baking would also have an effect.

With these four factors, I would have to make a minimum of four batches of dough – and that design would include some aliasing or confounding (Which means the statistics would a factor would be significant, but you can’t be sure if it’s a main effect or a two-way interaction, for example, in what’s called a Resolution III design.).  That number of experiments is not bad, really, but it’s more than I have room to store at one time.  And frankly, that’s a little more hassle than I’m up for right now with the little ones.

Minitab gives me this half-fraction factorial design (Resolution IV):

StdOrder RunOrder Blocks Recipe Butter Pan Cooled Dough

4

1

1

1

1

1

-1

1

2

1

1

-1

-1

-1

6

3

1

1

1

-1

1

2

4

1

1

1

-1

-1

8

5

1

1

1

1

1

3

6

1

1

-1

1

-1

5

7

1

1

-1

-1

1

7

8

1

1

-1

1

1

With an alias structure of:

I + ABCD
A + BCD
B + ACD
C + ABD
D + ABC
AB + CD
AC + BD
AD + BC
 

I’d also want to be considering blocking in the experiment, because I don’t see how it can be avoided without increasing the “costs.”  Blocking would simply mean, for example, that I’d be baking more than one sheet of cookies at the same time.  The cookies baked in that particular oven cycle have that same treatment that may differ in some ways from the other baking batches.  Identifying something like this helps assign known possible variation to this factor, rather than just adding it to the random variation (e.g. everything else not accounted for with the chosen factors).

There may also be a bit of an ethical dilemma that educational scientists and social scientists are really more familiar with than those of us in engineering or the “hard” sciences.  If you know a particular combination will short-change the subjects (in this case, make the cookies bad), should you go through with that “treatment?”  Okay, so burning cookies or making them crumbly to prove an experimental effect really isn’t much of an ethical issue, but it’s a good question to consider.  Even in the hard sciences, can your experiment be set up to avoid known failures?  (It can.  It involves changing the design space…)

So why, if I love experimental design – and cookies – did I not take this more extensive approach?  (This experiment would yield about 250 cookies.)  Perhaps some of the first questions an experimenter needs to ask is what is he or she interested in learning, what is the available budget (time, money, resources) for the study, and what is the value of the learned information.  Every world – the business, the lab, the home – must have priorities for the many demands facing it.  These limitations are part of what has driven the development of computer experiments that look to optimize the efficiency of designs, meaning finding designs that give you the most “bang for your buck,” or the most information for the minimum number of “runs.”

My thoughts were that I wanted to gather some information with some quick trials while avoiding a one-factor-at-a-time (OFAT) approach (which would likely make me fat, too), so I was interested in a sort of screening experiment.  For minimal costs, (the time it took to make one batch of cookies), I found a way to make the cookies stay together, discovered butter wasn’t the only issue, and found my insulated pans weren’t causing big problems, either.

The results? Delicious cookies, a happy family, and a more confident mama.  My husband and girls wouldn’t be super-impressed with my main-effects and interactions plots from Minitab or the p-value for any statistically significant effects.    Really, my oldest is still 2.  Maybe next year I’ll start showing her that stuff.  😉

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The Quest for the Perfect Oatmeal Scotchie – An Experiment

One day, I baked cookies, and the love of my life chose them as his favorite.  Oatmeal Scotchies.  They were something different and delicious.  He married me.

I tried often to make these cookies again, but they never seemed to turn out “just right” like they had that first time.  When I was working, my baking attempts at these were few, and remembering changes from one baking day to the next was not something that was working for me.  Sometimes, the cookies seemed to come out just right on non-insulated baking sheets, while baking on my regular insulated sheets produced too-crunchy cookies with many voids in them (which made them very crumbly).

I’ve actually avoided making these cookies for quite some time (though they are my dear husband’s favorite and my freezer was well-stocked with butterscotch chips) because I didn’t want the disappointment of another I-followed-the-recipe-perfectly-but-still-failed experience.

I was brave today.

A couple of weeks ago, we visited my parents at the start of our vacation, and Mom had made these cookies.  She had used the recipe from Nestle (printed on the butterscotch chips package) which calls for butter.  The cookies were DELICIOUS, but they also had the small holes in them that I had observed in my baking.  She noted that she never had that trouble with Aunt Viola’s recipe, which uses shortening.  She uses insulated baking sheets, primarily but not exclusively, just like me.

That comment got me to thinking, so today, I combined the recipes.  They are very similar except for the shortening/butter difference – and the flour and oatmeal amounts.  I had previously had a hypothesis (essentially, a hunch, but I’m a scientist, remember) that the oatmeal may have something to do with the voids.  (With one previous batch, I tried mixing by hand instead of using my Kitchen Aid to disperse the oatmeal.  I thought this may minimize air pockets near the oatmeal.  I didn’t notice any change with the results that time.)  I wanted to know if it really was a butter issue or something else.

So, I combined the recipes.  I also baked the cookies on both insulated and non-insulated sheets.  For one sheet, I refrigerated the dough for about an hour before forming the cookies and baking them (on an insulated sheet) to test a suggestion from a friend that all dough that has flour and butter should be refrigerated first before baking to avoid spreading.

Here are my observations:

  1. There were still a few voids in the cookies on both the insulated and the non-insulated cookie sheets, but nothing like what I saw previously.  These were hardly noticeable.
  2. The batch that was in the refrigerator before baking did not spread as much as the others, but I didn’t like this.  The others seemed to look more like “normal” cookies to me, flat and round instead of mounds.
  3. The non-insulated cookie sheet produced crunchier cookies and took less time to bake.  Again, I didn’t observe any significant differences between these and the insulated ones in terms of spreading or voids.

The real results came with my husband’s taste test.  “They’re perfect,” he said.

So, here’s my new family recipe for Perfect Oatmeal Scotchies. (With credit to Aunt Viola for the base recipe.)

Perfect Oatmeal Scotchies

1 cup butter
3/4 cup brown sugar
3/4 cup white sugar
2 eggs
1 teaspoon vanilla
1 3/4 cup flour
1 teaspoon soda
1/2 teaspoon salt
1/2 teaspoon cinnamon
2 cups oatmeal
1 package (11 oz.) Nestle Butterscotch chips

Preheat oven to 375 F.  Cream together butter and sugars.  Add eggs and vanilla.  Mix well.  In a separate bowl, combine flour, soda, salt, and cinnamon.  Gradually add flour mixture.  Stir in oatmeal and butterscotch chips.  Drop by rounded tablespoon onto ungreased baking sheets.

If using insulated baking sheets, bake for 9-10 minutes for chewy cookies, or until edges begin to brown.  For crunchier cookies, bake for 1-2 minutes longer.  (If using non-insulated baking sheets, shorten baking times by approximately 2 minutes and watch closely to avoid over-baking.)  Cool on baking sheets for 2 minutes.  Remove to wire cooling racks to cool completely.

Makes about 5 dozen cookies.

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