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What type of program for study

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  • #46844

    Sah
    Member

    I am a high school junior doing a study for Intel. My research involves comparing nutrigenomic based supplementation for methylation, measuring improvements in 2 lab values over time, and then measuring behavioral improvements over the same time period. Trying to prove that an improvement in lab values = improvement in behavior.
    N=will be 30. Have no idea what type of analysis I would do for this,
    Trying to make this as powerful as I can, as I can not do a control study so need it to be strong (I know it is, just have to prove it)
     
    Thanks for any suggestions/help
    Meg

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    #155420

    Allthingsidiot O
    Participant

    I may  suggest  to  apply  the “paired t-Test”,using  the  formulas:
    t=d/Sd/SRn & t=d(bar)-mu/Sd/SRn (SR stands  for  square  root).
    You  may  state H0: Mu1=Mu2
                             H1:Mu1 n0t  equal Mu2 (using  the  first  formula  above  to  calculate  the  t ),then  search  for  t(0.025,29) in  the  concerned  t-table,if  you  receive  a  higher  value  than  the  calculated  one  then you  conclude :fail  to  reject,if  below then  you   would  reject  H0 and  accept H1.
    Good  Luck

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    #155468

    accrington
    Participant

    I don’t quite understand what your question is. When you say you are measuring behavioural improvement, are you talking about people? If so, does N = 30 refer to the number of subjects in the study?

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    #155513

    Sah
    Member

    Yes 30 subjects measuring two lab values from pre/then post.So two values measured twice (start/end) Then a behvaioral assessment pre/then post(will be at the same time as the above values are obtained), the behavior  assessment measures 4 categories, but it will already be scored and a total then a subcore for each category. So a total score and 4 individual values pre and then again post on each 30 subjects.

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    #155538

    accrington
    Participant

    To clarify. Are there two different values that you are measuring in the lab, and are they continuous variables?
    For the beahvioural assessment, there are four categories, plus the total of the four categories. Are these continuous variables?

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    #155615

    Sah
    Member

    If you mean continuous, blood value MMA will be measured pre/blood value MMA will be measured post. ) Blood value B will be measured pre treatment then /Blood value B will be measured post treatment . Same value measured twice, but two different markers. (forgive my non statistical terms, only high school junior) All 30 subjects will be receiving the same substance.
    Then I would like to correlate the improvements in the 2 different markers in the blood to the behvioral assessment, which has a total score, but then will have a sub score measuring 4 different domains. The 4 subcatgories are:
    1. speech
    2. sociability
    3. sensory cognitive avareness
    4. Physical behavior
    Same questions pre test post test. Each sub category gives a numerical score, then all added for a total score.
     
    I don’t have the ability to do a placebo/double blind study with this population.
     
    Thank you for your help, and I hope this is more clearly explained.

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    #155628

    Sloan
    Participant

    This is a test with many moving parts so it is important to set up your experiment correctly to minimize bias as much as possible.
    You have a chain of hypotheses that must be tested along the way. First, you hypothesize that a given supplement will have a statistically significant effect on blood chemical A. Second, you hypothesize that the same given supplement will have a statistically significant effect on blood chemical B. You can test both of those hypotheses using a paired t-test as was previously suggested. You must run two seperate paired t-tests; one on blood chemical A before/after and one on blood chemical B before/after.
    After you have determined significance for each blood chemical of interest, you can do a correlation study to see if the change in blood chemicals correlate to the behaviors you outlined. I would expect that there may be a mild correlation, but I would expect a very large error component due to the small sample size and to the uncontrollable factors in the study.
    Good luck with your study, it sounds interesting.
     
     

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    #155646

    Sah
    Member

    Thank you for explaining how to set it up. Knowing my sample size is small, but one more question, what would be a statistically strong p value for a study like this, I know many errors, but just wondering?
     
    Thanks again

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    #155651

    Mike Archer
    Participant

    Hello.  I’m new in training, but I did learn that a 99% confidence interval is needed for any hypothisis test related to medicine or health.  That equates to a p-value of 0.01 or less to reject the null.
    Mike

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    #155671

    Sah
    Member

    Mike,
     
    THANKS! So far what I am getting is 0.01 so far so good. Phew! Three years on this and thought it would be no good. Would that p-value give my hypothesis more power? Even with such a low number of participants?

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    #155677

    Robert Butler
    Participant

      I don’t know the sources of the training material that would suggest that one needs a p value of .01 or less for the medical field.  I’ve been working in the medical field for quite some time and the cut point in all of the work I’ve done has been p < .05. 
      As for the question about p value giving the hypothesis more power – this doesn’t make sense.  The power of a test and the degree of significance of the results are not dependent on one another.  For the kind of work you are doing (we would call it a pilot study) the usual practice is to focus on alpha (look for results with p <.05) and recognize that, more likely than not,  the study will be very underpowered. 
      The reason for doing an underpowered study is simple – a pilot study’s primary focus is on trying to see if there is anything worth investigating.  Running an initial study with hundreds of mice/enrolled patients/volunteers etc. only to declare, with a power of .8 or .9, that there wasn’t anything of value is a waste of time and money and a sure fire way to guarantee a short career path in the world of medicine.
     

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    #155693

    Sah
    Member

    So in other words, this would be considered a pilot study, and if the alpha value is p<0.05  one would state the studies limitations due to size of sample, but that it might be worth larger study? Is that correct?

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    #155702

    Robert Butler
    Participant

     The short answer to your question is – yes.  When writing up our findings we report them in the following way:
      1. A simple table with the population demographics – that is a bean count for things such as age, gender, race, prior relevant medication, etc.
      2. If we have an effect with P < .05 we will report this and we will also use the sample statistics to give the reader an estimate of the power associated with our study.
     3. If the effect has a P < .05 and if the difference is clinically meaningful we will comment on its ramifications in the discussion section and we will also highlight the study shortcomings (size of sample, bias of sample, clinical issues not addressed etc.) and make recommendations concerning possible future work.
      Before going much further in your work I’d recommend you get a copy of An Introduction to Medical Statistics 3rd Edition by Bland and give it a reading. This is the book we use when introducing our residents/fellows to issues surrounding the use and reporting of statistics in the medical arena.

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