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Math Help - Stats - pairing or unknown o?

  1. #1
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    Stats - pairing or unknown o?

    Is this pairing? Or doing two samples with unknown variances that are not equal? They want a 90% confidence interval.

    Pesticides applied to an extensively grown crop can result inadverdent areawide air contamination. Ambient air samples were collected and alayzed at an orchard site for eac hof 11 days during the most intensive period of spraying. The levels of diazinon residue during the day and at night are recorded in the table (a whole list given). The researchers want to know if the mean diazinon residue levels differ from day to night.

    So... we are given data to work with. Is this pairing? Or is it just your regular two populations? Thanks!!
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  2. #2
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    If the subjects of your test remains the same it is pairing.
    For example if you apply the pest. to the crop and measured "before" and "after" for each test subject (crop) then it is a paired test.
    So, you should have exactly 2 data for each crop: before and after.

    But my feeling is that yours should not be paired t-test. You got to give us more info about the mechanics of your test and data collection to rule that out.

    -O
    Last edited by mr fantastic; February 7th 2009 at 08:01 PM. Reason: Removed link not relevant to question (looks like a signature but isn't)
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  3. #3
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    I wrote the question word for word, which is why I'm a little iffy. As you can see it's not clear. But the data, I did not write out. It was:
    Diazinon Residue
    Date Day Night
    Jan 11 5.4 24.3
    12 2.7 16.5
    13 34.2 47.2
    14 19.9 12.4
    15 2.4 24
    16 7.0 21.6
    17 6.1 104.3
    18 7.7 96.9
    19 18.4 105.3
    20 27.1 78.7
    21 16.9 44.6

    It also asked you to specify what assumptions you made. So I'm guessing I could do pairing, and say I assumed they were the same "species" being sampled. Although when I think of it... it's "air" being sampled... but in the same location I believe. ugh.
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  4. #4
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    Don't wanna mislead you but I don't think this is pairing. Because there is no "before-after" story. You are just measuring air particles (or whatever) in nights and days. The number of data points are equal but that is not enough for ruling out a paired test.

    All you need seems to be a two-sample t-test.
    If you get an F from this one please don't blame me.
    Just wanted to add my 2-cents...
    Good luck.

    -O
    Last edited by mr fantastic; February 7th 2009 at 08:01 PM. Reason: Removed link not relevant to question (looks like a signature but isn't)
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  5. #5
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    haha, alrighty. I'll do it both ways and ask the teacher before we hand it in. I'll swap it for the correct one. :-) Thanks!
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  6. #6
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    You're wicked
    Good luck.

    -O
    Last edited by mr fantastic; February 7th 2009 at 08:02 PM. Reason: Removed link not relevant to question (looks like a signature but isn't)
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  7. #7
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    outatime,
    I am now quite sure that yours should be a paired t-test. Because your "subjects" are actually days. You have two readings for each subject (daytime and night time). So there is a pair-wise data for each subject. Therefore, it does not make much sense to compare Monday's daytime reading and Tuesday's night.

    Sorry if I directed you wrong way, but I positive that it should be paired t-test. My apologies again...

    -O
    Last edited by mr fantastic; February 8th 2009 at 01:00 AM. Reason: Removed irrelevant link (looks like signature but isn't)
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