## Monday, August 20, 2007

### A Real World Math Problem

Many teachers seem to confuse "criticism" with "critical thinking", even though each is almost the antithesis of the other. Mike of EIA applied some genuine "critical thinking" to a news story he saw, and needs some math to make sense of it. Check out #5 in this week's Communique.

Tony said...

Uhh..Are we supposed to be describing a plausible scenario?

Mike Antonucci said...

Thanks, Darren. I've already received several responses, but they all contain equations that I have to test. I'll do that today and blog it. One math professor who reads your blog says there is no solution because the statements describe two different populations.

And Tony, even an implausible scenario in which the math works would suffice.

Tony said...

First, let me say that I had a hard time finding the statistics I would need to describe a plausible scenario. I will proceed nonetheless.

b) "about 24 percent of teachers nationwide have five or fewer years of experience."

this means only 76% of current teachers have more than 5 years experience. The NEA lists the total number of K-12 teachers at about 3 million, which translates to roughly 2.3 million "experienced" teachers, give or take.

a) "as many as half of new teachers in public schools leave before they hit the five-year mark"

Of the remaining 24%, or 700,000 teachers, only half of them can be expected to make it past 5 years.

It's hard to calculate the percent changes over time without knowing the attrition rates versus time teaching. Assuming even population distribution for years 1-5, which I know is unlikely, then the "experienced" group will increase by roughly 14,000 teachers a year, as half of the 5th year teachers cross the benchmark. The "new" group will lose 84,000 teachers a year (50% attrition plus successful fifth year survivors.)At this rate, about 115,000 new teachers need to be certified each year to maintain the 76%/24% split.

(2.3 million + 14,000)/(2.93 million + x)=0.76

x=115,000 teachers

The NEA claims that we will need 2 million new teachers over the next decade, which breaks down to 200,000 a year. This makes me think that my numbers are at least in the ballpark.