sample size

  1. U

    Sample Size Difference in Kruskal Wallis- big problem or little problem?

    I know Kruskal Wallis can handle "some" difference in sample size. but is comparing 3 set of data with the sample sizes n=170, n=139, n=44 going to throw things off too much? Thanks
  2. T

    Calculating Sample Size for a prospective/longitudinal study

    I am an undergraduate conducting a literature review. I am wanting to discuss sample size among the papers I am critiquing. The papers I am analyzing are studying hearing impaired populations over a given time, to discover whether they are more susceptible to cognitive decline. How do I...
  3. G

    Sample Size calculations with sub-groups

    I am in a situation wher we need to recruit 1600 people with a particular condition (calculated so that we can detect a 5% change following intervention). We also want to test the intervention on a particular sub-type (drug-users), where we expect a higher prevalence of the condition, and want...
  4. R

    Fractional Factorial Design Question

    Does anyone have experience with using fractional factorial designs for psychological research? I'm new to DoE, and I have no guidance except the internet... not too helpful. Anyhow, I have a practical question about data collection and entry (e.g. minitab) The question is: if I have...
  5. F

    random-effects regression in STATA

    I am looking at whether group differences (parkinson's patients versus age-matched healthy controls) exist in the performance of a perceptual task that has two DVs: reaction time and error rate and two stimulus exposure durations (preconscious and conscious). I have run the main analysis which...
  6. L

    proc power onewayanova

    Nevermind, I was not getting any responses :(
  7. L

    When to assume Normality

    I am working with a rather large sample (approximately 120). Typically, I would not have any issues justifying normality due to the large sample size and that the Central Limit Theorem would allow me to make that justification. However, of the 120 or so samples, there are about 8 extreme...
  8. S

    chi square test

    I am running a chi square test, followed by a marascuilo test to compare a binary resonse with categorical variables as the independent variables. The dilema is that my total sample size is 1,000,000 so I am getting chi square values in the thousands, with no major differences in the actual...
  9. R

    Help with power analysis!

    So, I've never taken a statistics course before. Just completed my honors thesis and graduated. Now I'm trying to do power analysis (post hoc) on my data. Using G power, please help me with what to do/how to interpret the results. First of all, I looked at two independent groups (group 1...
  10. S

    extremely small sample size

    I have a Y variable that is measured in parts per million (ppm). However, it can be converted to a binomial variable comparing against a p=.1. The problem is only 4 samples were collected, and the response of telling them to collect more samples is not possible. Is there any statistical test...
  11. D

    Required Sample Size Calculation

    First time forum user and STATS novice so I apologize on many fronts. I'm working on a customer survey to help forecast future product sales. We have current customer data for 2009 and 2010. From that we are trying to determine what sample size (number of surveys) we need to be able to...
  12. G

    Minimum Sample Size for a Survey

    Hi guys, Here's a question I've been struggling with over the past week. My employer would like to perform a survey to gauge public opinion on a number of government agencies. I'm trying to put together the concept and one of the questions I've run across has been "what would be the minimum...
  13. R

    sample size determination using a population range

    Hi. I have a problem about sample size determination. The population of interest is somewhat vague. What I know about the population is only the population range R, i.e, R = max value - min value in the population. I don't know the population distribution, also. Is it possible to...
  14. C

    Regularized Canonical Correlation Analysis

    Hi, I have a question about sample size and regularized canonical correlation analysis. Is a sample size of 15 unreasonable to use in a regularized canonical correlation analysis? If one has lots and lots of potential explanatory variables (multicollinearity expected) and multiple response...
  15. M

    cell size for multifactorial ANOVA

    Hello, I wonder if I could get help with this. I am analyzing data on scores from a psychosocial development assessment on young children, trying to see if there are any differences by their age, sex, location, and length of participation in a program. I’m using multifactorial ANOVA (using...
  16. L

    Reference for max vars in a model

    I used 7 predictor variables in a regression model with a sample size of 103. Someone who reviewed my manuscript said that was too many predictors. I thought the rule of thumb was that you should use no more than 1 predictor variable for every 10 observations. For example, no more than 5...