experimental design

  1. B

    Factorial Design

    Suppose a dermatologist wants to study the effectiveness of two different preparations of a skin lotion using two different forms of application (for example, one vs. two applications per day). He has available 12 patients with a certain skin disease and he can apply one form of medication (that...
  2. R

    Help with R GLM Formula for paired/nested model

    I have an experimental design as follows: Two treatments, carried out on the same sample. The samples are collected from soil at five depths, in five different pits, from five different fields. I want to: (1) see if the treatment has an effect on the species richness found in the soil...
  3. C

    Defining Contrast Matrix

    In the book Applied Longitudinal Analysis, 2nd Edition there is an example in the chapter "Marginal Models: Generalized Estimating Equations (GEE)" in "Muscatine Coronary Risk Factor Study" sub-section. I am illustrating it below : Let Y_{ij}=1if the i^{\text{th}} child is classified as obese...
  4. N

    1 DV w. four levels, 2 IV's

    I'm testing the predictive effects of mood (positive/negative) and personality traits (extraversion and neuroticism) on music preference (interest level in 4 different musical categories). This follows a between-subjects design. A positive or negative mood was induced via video...
  5. C

    Does Imposing a Constrain Make a Method More Powerful?

    Suppose we have 100 patients in a randomized trial. 50 of them are in treatment group and the rest are in placebo group. This is a longitudinal study so that we measure the response from each individual at four different periods: baseline, week 1, week 4, and week 6. Now suppose we have good...
  6. C

    Defining Contrast Matrix

    Suppose I have a binary Covariate X which is defined as X = \begin{cases} 1, & \text{if treatment group} \\ 0, & \text{if placebo group} \end{cases} The model is \mathbb E[Y] = \beta_0 + \beta_1X, where Y is a continuous random variable. If X=0, then \mathbb E[Y] =...
  7. T

    Is this Experimental Design even possible? Help please!

    Hello all, First thank you in advance for any and all help given in response to this question. I've been searching this forum as well as other places online and I'm still confused about what methodology I should use in this experiment. DESIGN: Participants are given two questionnaires...
  8. B

    Experimental design question

    I am struggling with the complexity of my experimental design... I apologize in advance for any incorrect terminology or grammar. I know that I have a 2x2x2 factorial design with 2 different dam diets (during pregnancy), 2 different offspring diets, and genders (obviously 2 levels)...
  9. G

    Regression analyses and replicates

    Hi, Thanks in advance for any insight!
  10. S

    Experimental Design Assignment

    I have an assignment that I can't solve in/with R I don't give the whole problem statement, but only the details that are of concern The objective of the study is to assess the ecacy of X (as compared to the reference treatment with SCALA). In this study 24 hills with grapevines are at...
  11. L

    please help: Is this R-syntax is true?

    I want to ask some confusing in my mind regarding the data analysis: I have conducting the experimental trial in repeated measure by hours as below: Design: Completely Randomized Design--(in green houses)-there are 6 box unit...
  12. K

    Which statistical test to use, 20 subjects, 6 categorical variable, 4 parameter

    Hi I have an experiment and are not sure which statistical test I should use. I hope some of you can help me, as this is not my strong side.. I have 20 subjects looking at 6 different categories of images, 40 trials per categori. I have 4 numerical variables I measure for each trial: 20...
  13. Y

    ANOVA issue with experimental design

    Hey guys; I am evaluating the effects that various factors may or may not have on the output of a process. Each of the factors has a different level. [http://i.imgur.com/8UhG4ri.png]Here[/http://i.imgur.com/8UhG4ri.png] is the general layout in tabular form My research group wants to see if...
  14. J

    is there interaction effect in RCBD with a single observation per cell ?

    The statistical model for a Randomized Complete Block Design (RCBD) with a single observation per cell is: y_{ij}=\mu+\tau_{i}+\beta_{j}+\epsilon_{ij};\quad i=1,\ldots ,a, \quad j=1,\ldots, b, where y_{ij} is a random variable that represents the response obtained on the ith treatment of the...
  15. C

    Stats Analysis Question =]

    Hey Everyone, Question!: In an aged-matched experiment, I want to compare . . . . I want to test the significance of DrugY on performance of Task1 for EACH child: (In this case each child is acting as their own control) Classic Autism DrugY Child A VS. Classic Autism Placebo Child A...
  16. J

    Looking for guidance on an experimental design

    Hey folks: I've got a question that requires a somewhat complex experimental design (nested + repeated measures) and wanted to get a few opinions. I am measuring soil respiration (essentially metabolic rate of microorganisms and plants underground) in a forest that has been damaged by a...
  17. W

    Nested/Repeated Comparisons-What test should I use?

    Hi! I am having trouble to decide what statistical test to use on my data because I have one factor grouped within another. Here is my experimental design: I have two cell lines, one infected with a bacteria (I) and one uninfected (U). I have split each of theses cell lines into two groups...
  18. C

    Experimental Design help

    Been running around in circles with this for a while. I am trying to figure what sort of design I have and how to go about analyzing it. Any help would be great. Details are below. Sample Date, 3 levels, fixed Field, 2 levels, assumed to be random from a larger population. For each sample...
  19. M

    Statistical test and power

    Thank you for your help! I am having trouble understanding what statistical test I can use, in order to figure out a power analysis. I want to prove that an animal is capable of vocally matching a stimulus. So I have a pre-recording of the animals call, a artifical call played to the animal...
  20. S

    Growth Curve But Not Repeated Measures Analysis

    I woke up this morning realizing that repeated measures was incorrect but my revelation did not go as far as to what was. Here is my experiment: I had 7 groups of 3 varieties of seedlings (experiment repeated twice). After approximently a month I would take data on one group of seedlings...