ancova

  1. S

    a good example of ANCOVA in R

    Hi, I was wondering if someone can provide a nice and quite complete example of ANCOVA in R. thanks :)
  2. L

    scatter plots with 2 covariates. spss

    Hi, I have two independent variable (location and season), one dependent (number of juvenile whales) and two co-variates (number of adult whales and length of longest whale). I know I have to do a ANCOVA, but I need to produce a scatter plot to compare the slopes of regression.... How? is...
  3. A

    non-parametric ANCOVA?

    Dear all, I would appreciate any help on a much debated issue of non-parametric ANCOVA. I compare 2 gourps (group is a factor, categorical), y is post measure, and x is pre mesure (covariate). The question is if the effect of the treatement is the same on both groups. Are there...
  4. K

    Should i use ancova or anova? One continuous variable and one categorical variable.

    I have one dependent variable that is continuous. It is the score on a particular achievement test. I have two independent variables. One categorical (three levels of ability) and one continuous variable (motivation) that is based on 6 likert items (ranges from 0 to 42). I want to find out...
  5. S

    SPSS ANCOVA Warning

    Can someone pls help me resolve this? Thank you SPSS Warning The large number of columns in the design matrix will cause integer overflow. The large number of columns may be due to too many levels in one or more factors, or to higher-order interactions among factors with many levels. It may...
  6. victorxstc

    Risk Factors in a Clinical Trial

    The study is confidential right now. So I cannot go into the details. But will try to detail every necessary information, in the hope that can get some good advice from you. The design is a clinical trial. We assessed the effect of a material on healing of oral wounds. It turned out to be...
  7. H

    Help in analysing pre/post stats in a repeated measures ANCOVA

    Hi all, I am currently trying to work out if it is possible to run a repeated measures ANCOVA in SPSS where the two levels of a factor are each tied to a seperate covariate. To clarify I have a study with a 2x2 design of timing (pre/post) and valance (good/bad). In the study the...
  8. B

    Need help (ANOVA & ANCOVA)

    I'm writing my dissertation and I used ANOVA and ANCOVA. After a lot of trouble, I'm finally writing the results. But I don't know how to put the values. Someone told me I should write "(ANOVA; F(x,y)= Fvalue, p= pvalue)". But what should I write instead of x and y? I thought x was degrees of...
  9. N

    ANOVA One-way Vs Factorial ANOVA. Discordant results.

    Hi everybody, I have to investigate the influence of many categorical factors (A,B,C) on a continuous response variable (Y). The procedure I'm following is: 1) Make three One-way ANOVA, every time with a different predicotor A, B, C) 2) Make all the three possible ANOVA two-way using the...
  10. A

    Appropriate to use time as covariable in ANCOVA?

    Hello stats people, I need to assess whether the rate of increase (in soil carbon) differs significantly between two groups (forests). I believe ANCOVA is appropriate for this, but am not sure. Independent variable: Forest Dependent variable: Soil carbon Covariable: Time since planting...
  11. O

    Factors in an nls model

    Hello, I have some nls model fitted with a four parameter logistic curve. model<-nls(V1 ~ SSfpl(V2, a, b, c, e)) I want to test the effect of a factor on this fit, something like: model<-nls(V1 ~ SSfpl(V2+factor, a, b, c, e)) or model<-nls(V1 ~ SSfpl(V2, a, b, c, e)+factor)...
  12. T

    how to calculate adjusted standard error to report with adjusted means for ancova

    How to calculate adjusted mean and adjusted std error? I'm using regression as ancova in R as below. Condition is coded: 0 = control, and 1 = experimental. I understand that the intercept is the adjusted mean for the control and the intercept + condition coefficient is the adjusted...
  13. T

    How to calculate adjusted mean and adjusted std error using lm()

    I'm using regression as ancova as below. Condition is coded: 0 = control, and 1 = experimental. I understand that the intercept is the adjusted mean for the control and the intercept + raw condition coefficient is the adjusted mean for the experimental group. My question is, can i...
  14. W

    Covary out?

    Hi all! Thanks in advance for the help! I have three variables A, B, and C A is an independent, two category variable B is an independent, continuous variable C is a dependent, continuous variable. I want to check if there is a relationship between A and C (i.e., are there...
  15. M

    ANCOVA violating assumptions

    Hi, The data I'm looking to analyse is vigilance data from monkeys. I need to investigate which factors affect the different types of vigilance. The first category I'm looking to investigate is "no vigilance" and therefore this is my dependent variable. This data includes a fair few 0's...
  16. G

    Power Analysis for 3 (between subjects) x 3 (within subjects) ANCOVA - How to

    Hi Stats Community, I'm so pleased to have discovered this resource. I'm having a lot of trouble with my power analysis for my proposal. I'll be doing a 3 x 3 mixed ANCOVA with two covariates. I've used G power but I don't think it takes the repeated measures factor into account, which I think...
  17. E

    Ancova repeated measures changing covariate

    I have a three factorial 3 by 3 by 3 data set, where all three independent variables are repeatedly measured. For each of the 27 conditions I have also measured a covariate. How can I ran this three factorial design within SPSS GLM or MANOVA. So far I found only solutions for a constant...
  18. G

    MANCOVA interaction effect

    Hello everyone, I am facing the following problem: I conducted a MANCOVA to investigate whether a control group significantly differs from 2 other experimental groups with regard to 4 different dependent variables. There was a covariate included which was supposed to moderate the relationship...
  19. K

    Question about using ANCOVA and reporting in a paper

    Hi All, I have a 3 (gait speed) x 8 (trials) within subjects experimental design and have submitted the manuscript to a journal. I was given revisions to do on it and re-submitted and have received revisions again hence my question... I have 14 subjects that walked for 35 minutes on a...
  20. K

    repeated measure ANOVA and covariate

    There are 55 subjects measured in two stages. The variable is called V1. There is another variable called V2 (dichotomies). Some values of V2 are different in Stage 1 and Stage 2. I want to compare means between V1 and V2. Normally, I can use one way repeated measures in SPSS. In addition, I...