date: Mon, 23 Jun 2008 18:03:50 +0100 from: Steve Jones subject: Significance testing results to: Tim Osborn Hi Tim, As we discussed in our meeting last week, I've recreated my contour comparison figures with significance testing, to show where differences are significant at the 95% level. I've put the figures here: http://www.squaregoldfish.co.uk/sekrett/figures.html To calculate the significance, I used a simplified t-test algorithm that can be used for scenarios where both data sets have the same number of values. I found it on (dare I say it) Wikipedia (http://en.wikipedia.org/wiki/Student%27s_t-test), but I did some quick comparisons between that and the one in the book you gave me, and they came out with the same results. The slightly disappointing result of from the comparisons is that the changes in the subtropical jet stream between 20cm3 and sresa1b (shown in sresa1b_winter_comparison.eps) are not deemed significant, even though the average wind is around 6m/s stronger in all the models. Since this is the largest change seen between the different data sets, it's a shame that it's not significant, and we therefore can't legitimately infer anything from it in terms of changes to the NAM. Is there anything I should do about this at this stage, or should I simply state what's there, and not analyse it further due to the lack of significance? Steve.