1. A

    Time Series - how to draw a sample?

    Dear all, This is probably a stupid question. But do you know how to draw a sample from my dataset? For example, if I want to only test the first 100 dates? I want to do this first, then I will test another 100 dates, so I don't want to change my dataset. I tried: arch var1 var2 var3...
  2. H

    Sampling methods, which is more appropriate?

    I have been collecting data on the temperature in an experiment for the last couple months, and I'm interested in the rate of temperate changes. The total amount of data is extremely large, and takes a long time to process, even using multi-threaded code. Currently I'm doing option 1, but I'm...
  3. L

    Statistics- Sample proportion?

    According to a 2010 report, 85 % of women in NA shop online. 1) Describe the population of interest 2) Describe the population proportion of interest in words. What value are we assuming for this proportion? 3)Determine the sampling distribution for the sample proportion of NA women who...
  4. E

    Duplicate sample probability

    I have a population of N unique items, and I take n random samples (with replacement, so some items may be sampled more than once). If I then take another n random samples from the same population, what is the likely percentage duplication between the samples? As n exceeds N by a long way...
  5. H

    Analyzing a sample list of numbers (median, quartiles, box plot)

    If you have a sample of 36 numbers (and some of these numbers are repeated more than once), how do you find the median, upper quartile, and lower quartile of the sample? Also when drawing a box plot, do you disregard when a number is shown more than once and just put it down once in the plot...
  6. X

    Difference between sample and population

    Now, in this case, will the given data for each group considered as sample or population ? I want to calculate SD, MD and Variance and i am getting confuse shall i consider it as a population or sample.
  7. L

    Testing the significance of differences between means of two samples.

    Hi, I am currently working on an event study that compares domestic and cross border mergers and acquisitions. I have gathered two samples one for domestic (3050) and one for cross border transactions (2040). Both of the samples were selected using same criteria with respect to announcement...
  8. L

    Sample size of Categorical Variables

    Hi, I'm running a binary logistic model that includes categorical variables. One of my main covariates has 8 categories and some of the sample sizes within categories are small (e.g. 25 people) but this is in a total sample of 8,537 people. However when you restrict it down to the...
  9. R

    Power calculation in Critiquing Tool

    Hi all I am currently trying to critique some orthopaedic research papers using the Downs and Black (1998) critiquing tool, but I am completely confused by the final question. It asks: “Did the study have sufficient power to detect a clinically important effect where the probability value for...
  10. M

    comparing frequencies

    I have a survey question that asks which of 3 activities participants regularly participate in. They are told “select all that apply.” So they can mark any or all of the activities. As results, I get frequencies (# and %) for each activity. Now I want to compare the frequencies of the...
  11. A

    sample distribution of residuals

    Find the sample distribution of the residual r = y - XBhat under normal regression model assumptions.* * I think this means to assume errors are indepedent, have mean 0 and variance sigma squared, are are normally distributed. Please help! Are residuals not just realizations of the errors and...
  12. R

    Discussing a model design

    I am a software developer and like stats but no professional so I would like your opinon on how to build a concrete statistical model the goal is to understand what are the most eaten foods in Austria I would like to know what you think of my approach: I go to a supermarket and observe the...
  13. M

    personality psych)self-selected sample bias = smaller variability?

    Context: online personality survey (BFI) for age 10~65 ( Measure taken: the authors tried to control for possible self-selection bias in the sample by "by examining the variability of Big Five domains and facets in...