Stats Made Easy

Practical Tools for Effective Experimentation

Thursday, November 20, 2008

Roasty toasty in Puerto Rico

I am enjoying a week of teaching class in pleasantly warm Puerto Rico (consider what it’s like in Minnesota this time of year!) and their servings of thick coffee with real cream and sugar. Normally I drink it black, but here I’ve been asking for el café con leche y con azúcar. One of my students, Jorge Nieves, gave me the heads up on some good PR coffee brands. He should know from growing up on a coffee plantation. Here are Jorge’s recommendations: Garrido Expresso, Alto Grande and Yauco select. The Yauco website says that the “University of Puerto Rico scientists studying the proximity of our farms to the Caribbean Sea theorize that micro nutrients are brought from the sea to the farm by the Alisian winds.” I cannot find anything on “Alisian” winds, but they feel good wafting in on my beachfront balcony!

Jorge explains that one must pay more for Puerto Rican coffee due to the relatively high cost to harvest the beans. The cherries (like the ones I pictured at a botanical garden outside Tampa) must be hand picked. November is the peak of production in Puerto Rico.

It seems to me that for this luxury of life the premium cost may actually add to its luster. However, Puerto Rican tourism officials may be overdosing on caffeine to think that their recent initiative for promoting coffee tourism will lure visitors inland from the lovely Caribbean beaches. On the other hand, how about a "surf and turf" vacation? That sounds good. After soaking up enough sun on the sand, then head for the hills and hit the haciendas. Now you're talking! (I really should call it quits for the day on drinking coffee.)

PS. Here are some interesting stats on coffee that I read in my airline magazine* while en route to San Juan from Minneapolis:
-- Coffee is known as “Joe” due to the US Secretary of Navy who in 1914 banned wine from officer’s mess – leaving only this hot, stimulating drink as an option.
-- It’s estimated that 1.6 billion cups of coffee are drunk worldwide every day. However, because the volume of a “cup” varies, no one can say how much coffee this really is!
-- The name Coffee is derived from “Kaffa” – a region in Ethiopia where in AD 800 a goatherd noticed his flock frolicking more than usual after eating certain berries. Fill in your joke here.
-- From Ethiopia “Kaffa” became the drink of choice for Arabians and then Europeans. A Dutchman established a plantation in Java in 1696 – hence that became a nickname for this stimulating drink.
-- Brazil is the leading country for coffee production -- 36 million 60 kg bags per year.
-- The manufacturer of Barcalounger claims they introduced coffee to the American workplace about a century ago in Buffalo. Didn’t they also invent spicy chicken wings?
-- Coffee seems destined to continually rise in popularity for the USA as evidenced by an increase in consumption by 18 to 24 year olds from 2.5 cups in 2005 to 3.1 in 2007 and 3.2 for 2008. ** (Americans measure a cup as 8 ounces – that’s nothing!)
-- The average American consumes 300 milligrams of caffeine per day.
-- Does drinking coffee help you stay awake behind the wheel? A French study measured the number of times coffee-drinking drivers crossed the center line. Those who took it decaffeinated crossed the line 159 times versus only 29 by the ones who kept the jolt in their Joe. Viva la difference!

*Source: “The Power of Joe” by Nancy Oakley, Delta’s Sky magazine, November 2008 .

** To counteract this assertion, I offer this anecdotal evidence: In the population of my 5 offspring and 2 in-laws – all younger than 30 years old – only one drinks coffee. The others go for caffeinated soft drinks (300 mg at least every day, I am sure!).

Friday, November 14, 2008

Where to draw the line on old wine

Several years ago I gave a talk on design of experiments at a national conference of microbiologists in California. One of the other speakers in my session was an enologist (a scientist that deals with wine and wine making) from UC Davis – Associate Professor David Block. He helped me settle a debate in my family on how long one should keep wine stored after opening. Opinions ranged from indefinitely (years!) to less than 3 days as a guideline. My guess was 10 days at the max.

Naturally I thought of ways to put this to the test. My idea was to try a triangle tasting over time. Each taster is given three wines, two of which are the same. I saw this in a book I am read called The Drunkard's Walk, How Randomness Rules Our Lives. (By the way, the author thinks professional wine ratings are nonsensical for the most part -- purely random.)

However, after hearing from Prof Block, who like me is a U of Minnesota chemical engineer, I may not bother to experiment on aging wine because his answer fits my preconceptions (warning: technical details ahead!):

“The aging of wine is mainly related to the amount of oxygen in the bottle after it is opened, the amount of SO2 used by the winemaker for that particular wine, the wine pH, the amount of phenolics (more in red than white wines), and the amount of previous oxidation. So, for instance, if you only drink a small amount and put the bottle in the refrigerator, you are likely to see less oxidation than if you drink almost the entire bottle and leave lots of head space in the refrigerator.

My experience is that with sweet, dessert wines, I can leave them for months and they are still OK. This may be due to the winemaker adding more SO2 to decrease the chances of growth on the residual sugar. The SO2 can protect the wine somewhat from oxidation and production of aldehydes (typically associated with off-flavors or aromas).

Something like a sherry can be kept for a very long period of time at room temperature, typically because it is already oxidized during long barrel storage necessary to get the sherry-like characteristics (e.g. butterscotch, carmel, dried fruit aromas).

The effects of phenolics are a little more difficult to describe as they can be oxidized themselves, liberate H2O2 in reaction when they react with O2 (that eventually produces aldehydes), etc. However, it is generally felt that red wines with higher phenolics will last longer than white wines with lower phenolics. And...of course, all of these reactions are sensitive to pH and temperature.

That's kind of a complicated answer to your straightforward question...but it is a pretty complicated system. I keep off-dry white wines in the refrigerator for months. Dry reds and whites...probably less than a week. Sherries and ports and brandies...more or less indefinitely at room temperature.

Remember, that different people have different abilities to taste and smell various aromas and flavors, so one person's acceptable period may be different than a second person's period.”

So for the dry red wines I enjoy (tonight it is a boutique Syrah from Paso Robles California), I drink up the bottle within one week. That's my theory (with support from Prof Block) and I am sticking to it!

PS. Wine is fine for sipping and entertaining at the fancier soirees, but for an old-fashioned backyard barbecue it’s hard to beat a can of cold beer. The trick is keeping your brew cool on a steamy summer evening. Check out the results of this very enterprising and creative beer drinker who experimented on can cozies . The one made of rice krispies is unusual but I’d bet on a Thermos brand can insulator like this one that claims to keep your beverage cold ten times longer and 3 times longer than foam cozies.

Thursday, November 06, 2008

Presidential polls perplexing

Last week I heard interviews of top pollsters by a public radio host who could not accept that their results could vary so much – from a margin of 14 percent for Obama to only a 1 percent edge over his opponent McCain. Clearly these predictions differed significantly. Given the power of statistics, how could that be?

The main reason from what I gathered was the variation in pollster’s models on who will actually vote. For example, as I reported in my blog of 12/31/05 (“Surveys produce precisely inaccurate findings”), about 60 percent of self-stated voters did not cast their ballot in the previous election. This attrition rate historically varies by party (Democrats tending to slack off more than Republicans, perhaps) and demographics. Furthermore, people are more and more resistant to being polled – two out of three now refuse according to an article by Rick Montgomery of McClatchy Newspapers (11/2/08). Furthermore, the demise of landline phones in favor of mobiles makes it ever harder to even contact prospective voters. Who wants to burn up precious cell time on a poll?

Amazingly enough, despite all these difficulties in coming up with accurate predictions based on pre-election surveys, the political snapshots proved sharp according to Ken Dilanian of USA Today (11/6/08). Despite dire warnings by analysts such as political scientist Steven Schier of Carlton College (Northfield, Minnesota), I suppose that since all of the polls correctly forecast a win by Obama (his margin was 6 percent – in the middle of the pre-election range of predictions), the statisticians will get by with the usual excuse of “random variation – the old bell curve,” as Scott Rasmussen of Rasmussen Reports put it. Hopefully they learned some things that will lead to better models next time on who will actually vote, how unreachable cell phone users vary from readily-accessible ‘land-liners,’ and the behavior of the silent majority who refuse to answer any questions. Good luck and please take me off your call list.

PS. One of the more interesting statistics I heard about voting is that for every 1 inch of rain in any voting precinct the Republicans gain a 2.5 percent edge! Maybe McCain’s supporters should have invested in fire trucks to hose down voters waiting in line to vote.