Milk update 5/20

Submitted by bandstra on Fri, 2011-05-20 17:35

5/20 (5:35pm): A milk sample with a Best By date of 5/23 was added to our Milk results. We have our fourth non-detection of I-131 in milk. The latest data point for Cs-137 is slightly higher than the previous one, but within error bars, the trend continues to be a decline in both Cs-134 and Cs-137.

Mark [BRAWM Team Member]

‹ Some of the current issues with the plant 5/20 Rain update 5/20 ›

thanks so much!

Submitted by Bill (not verified) on Fri, 2011-05-20 21:38.

As I suspected, the cesium 137 is staying around for awhile in the food chain. I would guess that the percentages will fall as the radiocesium is "washed out" by clean rains and by dispersion into the soil. But i do not expect the amounts to really be totally eliminated for some time.

Does that sound correct to BRAWM team?

Thanks, Mark

Submitted by Anonymous (not verified) on Fri, 2011-05-20 17:41.

Please excuse my ignorance. But, what do you mean by "error bars"?
Do you mean margin of error? If so, what is the margin of error?

Thanks again!!!

Apologies for the jargon

Submitted by bandstra on Fri, 2011-05-20 19:03.

Apologies -- I used some science jargon when writing that summary. Error bars and margin of error are basically the same statistical quantities. The main difference (I think) is that margin of error is usually used for measurements of percentages, such as in polling ("55% of people agree, with a 3% margin of error," etc.).

Error bars are the same thing, but have a more general meaning. An error bar tells you "If I made this measurement many more times, in what range would 68% of the measurements fall?" If you look at our plots, the error bars are the little T-shaped appendages above and below the data points.

There is a slight increase in the last measurement, but the increase is smaller than the uncertainty (error bar) of the number itself. The previous result had been 0.23±0.02 Bq/L, and the new one is 0.24±0.02 Bq/L. Since the increase is only 0.01, and the uncertainty is 0.02, that is not enough evidence to say that it is really an increase.

It is also not enough evidence to say that the downward trend has stopped, especially given that the Cs-134 measurement decreased (the two should closely track with each other).

Does that clear it up?

Mark [BRAWM Team Member]

Well, I had to take

Submitted by Anonymous (not verified) on Fri, 2011-05-20 22:14.

Well, I had to take statistics twice in college.
This sure brings back memories.
You're a good guy, Mark!

Yep. Much clearer

Submitted by Anonymous (not verified) on Fri, 2011-05-20 19:10.

Thanks for the explanation, Mark.