# How do you calculate change in concentration of a specific subset of a population?

Asked by

mmkg79 (

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)
July 29th, 2009

I am trying to figure out the change in concentration of a specific population. For example, in 2000 there were 1,870 students 58 students were a minority. In 2006 there were 2,192 and 83 were a minority. What is the change in concentration of minority students. I know the percent change (new value – old)/old; but I am trying to figure out if the concentration has increased b/c the total population has increased.

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## 7 Answers

Statistics can be a bear, right?

Whenever you’re doing percentage work, make sure you keep asking yourself what the percentage is OF—that is, this figure represents X% of *what*?

Here you need to figure out concentration—so if I have 20 students and 1 of them is Pacific Islander, how would I figure out the concentration of the Pacific Islander students in the population? Once you have the concentrations for each year, then you need to figure out a way to compare the concentrations each year (hint: that’s really, really, easy).

You’re close in thinking percent change, but remember, what is that figure a percentage of? There you’re looking at the percentage increase of minority students between the two years—but the percentage doesn’t have any relation to the larger population. Not really what you’re looking for.

Still a little confused. After I get the percentage for each year I just subtract the new percentage from the old percentage to get the change in percent?

Close. Subtract the old from the new. A positive number means a gain in concentration and a negative number means a decline in concentration.

The portion of the population that is minority increased by 0.68%, a 22% increase in minority concentration between 2000 and 2006. It’s kind of interesting. What caused such an apparently rapid increase in minority concentration?

What population(s) do these data represent?

One easy explanation is that the classification system may have changed so that more people are classified (or self-classifying) as a specific minority. Yet another is that there has been an influx or increased growth of that minority in the local population on the whole.

Thank you daloon (and others). I came up with the same answer too but didn’t know if it was correct. The data represents a small school district North of Minneapolis. We are looking at 10 school districts. The combined increase in minority for all 10 school districts was 73%.

In 2000 your minority students make up 3.1% in 2006 it was 3.7%. Is that significant? Probably not. There is usually a statistical variable of at least +/- 1%, that is if one of the statistics increases/decreases by 1% no real finding can be reached.

For example in @mmkg79 original example, if the increase in minority students was 25 out of 312 increase ln all students or 8% OMG! we’re turning into an inner city school district. Order the cameras and metal detecters.

What if the reality is that a new Japanese auto company came to town with 4 executive families/4 children and they will be leaving w/i 5 years. A newlywed African-American doctor arrived in 2001 and they had quadruplets. The new Baptist minister named Martinez awas hired and his 5 Spanish surnamed children came with him. (BTW his family has been here since the conquistadors, he doesn’t speak Spanish and he met his blonde, blue-eyed wife at Oral Roberts University.) Mr. Liu and his wife and 3 children opened a Chinese restaurant like the one his grandfather opened in Dubuque 40 years ago. The rest of the new students are children and grandchildren of the 2000 minority families.

OR

The government has settled a large number of refugees from the war in Darfur.

With statistics raw numbers and %‘s are worse than useless because erroneous assumptions waste time and really don’t tell you anything. The only reason for a school district to do a statistical study of this sort is to plan for student needs, and that takes different statistics.

In the 1st case you may have to develop a Gifted and Talented program or contract for distance learning AP classes in lots of subjects, You may have to hire a college counselor.

In the 2nd case you may have to hire bilingual and ELD teachers. You may have to hire a counselor trained ti deal with . PTSS and cultural issues. You will probably have to expand food services and tutoring, maybe even evening classes for adult English.

Unfortunately school districts use meaningless minority statistics to get money that flows into the general fund instead of meeting real needs

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