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Thread: Pseudoreplication for my PhD Thesis: any advices?

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    Pseudoreplication for my PhD Thesis: any advices?




    Hello to everybody, that's my first post in the forum.

    I apologize for i) my bad english and ii) for the lenght of the post

    _______________________

    I have some doubts concerning the experimental design for my PhD thesis.

    As you can see from the picture attached I'm going to compare three different land management in three different areas: (i) plain, (ii) hilly, (iii) mountain trying to investigate the level of CO2 emission for each management option (pasture, wheat ...).

    I'm not a statistic expert but since soils are not comparable between plain, hills and mountain, I think I need to perform ANOVA inside each area and NOT between the areas.
    And I assume each field is infact a "treatment". So I'm going to perform pseudoreplication because wheat soil crop is a... subsaple of wheat soil.


    By the way my main questions are:

    i) Was I enough clear?

    ii) As you can see from the picture, one grey square = to a repetition. So I have 3 repetition per field (treatment). How many (pseudo) repetition for do I need to make sure my analysis will be statistically strong enough?
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    Re: Pseudoreplication for my PhD Thesis: any advices?

    I'm not a statistic expert but since soils are not comparable between plain, hills and mountain, I think I need to perform ANOVA inside each area and NOT between the areas.
    Yes, soil type and area are confounded. But at least you could
    compare emissions from pasture between the three areas.


    Or maybe you assume you have 8 conditions and compare
    them within one analysis. Depends on theoretical considerations
    beyond statistics.
    And I assume each field is infact a "treatment".
    Seemingly, each field is 1 case or "subject" in the analysis?

    With kind regards

    K.

  3. The Following User Says Thank You to Karabiner For This Useful Post:

    Muzzé (12-29-2014)

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    Re: Pseudoreplication for my PhD Thesis: any advices?

    Quote Originally Posted by Karabiner View Post
    Yes, soil type and area are confounded. But at least you could
    compare emissions from pasture between the three areas.


    Or maybe you assume you have 8 conditions and compare
    them within one analysis. Depends on theoretical considerations
    beyond statistics.

    Seemingly, each field is 1 case or "subject" in the analysis?

    With kind regards

    K.
    I'll try to explain me in better way: Areas (Hills, plain, mount.) are separated. I would like to perform CO2 emission analysis between the crops inside each area.
    Analysis will be performed twice/month in 365 days.

    So, Let's say I have just one area. Maybe the correct question is: --> how many sampling points per crop do I need to have?

    30 in crop 1, 30 in crop 2, 30 in crop 3?

    _________

    PS: Crop 1 is wheat, so it belongs to the same popolutation, so 30 sapling points are NOT 30 replicates, but 30 psuedo-replicates... I guess...
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    Re: Pseudoreplication for my PhD Thesis: any advices?


    Quote Originally Posted by Muzzé View Post
    I'll try to explain me in better way: Areas (Hills, plain, mount.) are separated. I would like to perform CO2 emission analysis between the crops inside each area.
    Analysis will be performed twice/month in 365 days.

    So, Let's say I have just one area. Maybe the correct question is: --> how many sampling points per crop do I need to have?

    30 in crop 1, 30 in crop 2, 30 in crop 3?



    _________

    PS: Crop 1 is wheat, so it belongs to the same popolutation, so 30 sapling points are NOT 30 replicates, but 30 psuedo-replicates... I guess...

    You could try an ANCOVA controlling the effects of your confounding variables(soil, etc...)

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