From: Marialena Nikolopoulou [mailto:absmn@bath.ac.uk] Sent: Tuesday, May 13, 2008 7:03 AM To: 'Jan Kleissl' Cc: 'Paul Linden' Subject: RE: sample strategy Dear Jan Your question is vey valid. We already discussed most of these issues with Samer and JC when we did a test run last week. They promised they would inform the others accordingly and get them to perform test runs within the group before going out. It might be worth checking that they have actually done so, otherwise it will be confusing for them and the public. The variance in the surveys will probably be as a result of all the points you mention. In terms of weather conditions, as sunny are the predominant conditions, I would imagine most of the surveys would be with that weather and shouldn't worry about it. I remember you mentioned that frequently it's overcast in the morning clearing up by midday. As we should be aiming for different times of day as well, from early am till pm, e.g. till about 5pm, this might cover a variation of weather conditions as well. With the students I was also talking about some standard points they should use for the reference group (i.e. the 5 students that that will be used for the longitudinal surveys). That means they should have around 5 standard points (in the wider EBU-II site) to evaluate at the different time periods. E.g. in shade, in sun, in a wind exposed area, by the bus-stop (hopefully with the bus arriving), etc. They should stay in each area for 5-10min before attempting the questionnaire so that they are adjusted to the local microclimate. They should do these points e.g. early morning, mid-morning, noon, early afternoon, late afternoon. This alone would give 25 questionnaires at each sampling period, for 5 times a day, it would be 125 per day. They could also move between different sites if it's not too much trouble for them. I.e. once finishing with one site they could try the second one, but check what their stamina is as well. It's really important that the questionnaires of the reference group are easily identifiable from the rest, so that they two are not mixed up. Could either use coloured paper, or they could write their names at the very top, so that the papers will not get mixed up with the rest of the surveys. It's probably worth keep repeating to them that they need to have their watches synchronised with the clock of the datalogger, so that the time period they mention in the survey sheets is the one that the data logger is recording. Another point worth repeating is to ask the questions EXACTLY as they are, with the choice of answers AS PRESENTED. There is a tendency to slightly change the phrasing according to the discussion as it's developing. That is a general worry irrespective of location. Also, when the public replies with "fine" or "ok", specify it in terms of the answers provided, e.g. fine on the warm side, neither warm nor cool, etc., while also not leading questions. I.e. should not ask the questions as if expecting a specific answer, it is important for the public to feel that there is no right or wrong answer, it is a personal choice and any answer is acceptable. We have discussed all these issues with Samer and JC, so they should be aware of these issues, but remembering them may be another story, which is why it is worth reminding them. If you have the portable station, it' probably best to put the station next to the standard group each time, so that they are evaluating what the station is directly recoding. Let me know if I have confused you even more or anything else you may need. Good luck, M. PS1 I'm a bit worried about whether there will be any difference on the PM10 readings between the different sites. Would you mind keeping an eye on the readings and if after a couple of days there are no differences in the readings trying a different site? e.g. use standard groups of students downtown in a more polluted site? although I appreciate that finding a polluted site is rather difficult in san Diego... PS2 Attached are the questionnaires with the maps for the two sites and the ethnic origin as discussed yesterday. I have not included the sunscreen question after all because it will greatly depend on whether it is arms, face, etc. so that on its own, would not help us with the findings (plus it is really tight in terms of space). -----Original Message----- From: Jan Kleissl [mailto:jkleissl@ucsd.edu] Sent: 12 May 2008 18:34 To: 'Marialena Nikolopoulou' Cc: 'Paul Linden' Subject: sample strategy Dear Marialena, What sampling strategy would you recommend? I am mostly wondering whether the variance in our surveys should come from the locations, the weather conditions, the respondents, or all of them? The more variation the less sample size per case. - weather conditions: should we get a large number of samples for one type of conditions (sunny) or should we spread it out over a range of conditions (sunny ? - time of day: always the same time of day or spread out over early am / noon / night? - I'll meet with the students on Wednesday and we'll shoot for taking a large number of surveys next week. Specific instructions for the students would be appreciated. Cheers jan