population

  1. S

    Proper Sampling - Can i sample like this without destroying reliability?

    The population that i need to extract a sample from is all firms from country A with activities in country B. The firms are classified into two categories: as having a subsidiary in country B, or not having a subsidiary in country B (the activity could then be exports, which does not require a...
  2. R

    Not sure about what test....

    Hi everybody, I need to analyze possible differences in the invertebrates populations living in 3 different environmental treatments (3 plus 3 replica). A subsample containing invertebrates species is taken every week for a total of 10 sampling events. Therefore 10 invertebrates populations...
  3. R

    Which test to be used?

    Hi everybody, I need to analyze possible differences in the invertebrates populations living in 3 different environmental treatments (3 plus 3 replica). A subsample containing invertebrates species is taken every week for a total of 10 sampling events. Therefore 10 invertebrates populations for...
  4. H

    Sample distribution of means and the minimum number of samples/population size

    Hi, Im having some issues with 2 things, and would appreciate it if someone could clear things up. (1) Ive read that the mean of "the sampling distribution of means" is the same as the "populations" mean. To construct the sampling distribution of means, i need to take X * number of...
  5. D

    Confidence intervals, proportions

    A simple random sample of 1000 New Yorkers finds that 87 are left-handed. (a) Find the 95% confidence interval for the proportion of New Yorkers who are left-handed. The answer my professor gave and the answer that I got are completely off from each other. Here is what I have so far n = 1000...
  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. M

    Model comparison in psychophysics with multiple participants

    Hi, I have a quite general methodological question about model comparison. I ran a psychophysical experiment in which each participants performed ~500 trials of a perceptual decision task. My observation are reaction times. I want to compare several possible model to find which one explains...
  8. L

    Descriptive Summations

    How would I go about solving this? 1/nΣxi^2=100 and 1/nΣxi=2. Define yi=2xi+1 and find 1/nΣyi^2.
  9. G

    Deciles and zero values

    Please excuse what may be a simple question, but i am not a big stats person. I'm calculating the decile breaks for a large set of data, 74k records. It's population data for US census tracts. I'm using excel's percentile.inc formula, so in other words, =PERCENTILE.INC(C$2:C$74134,0.1), etc...
  10. C

    Minimum sample size

    Hi Everyone, I have spent hours on this and cannot seem to get to the answer. Here is the questions: Calculate the minimum number of children that will be needed in the study to allow paired and unpaired analysis to be performed based on the the following assumptions. First, it is...
  11. B

    Population subgrouping analysis

    Hi all: I have a population consisting of 1000 different individual plant varieties collected from different latitudes (i.e. the geographic coordinates specifying the north-south positions on surface of Earth). We have generated close to 3000 molecular data points for each of the individual...
  12. L

    Hypothesis testing - which method to use?

    Hi everyone, I am taking a introductory Statistics course for my business program. I have been given a case to work with and I am completely confused about it. A little help would be great! I am not looking for exact answers per say, but just some guidance on which methods to use. Here is the...
  13. D

    N vs N-1 in variance of population?

    I did not get the why there are N and N-1 while calculating population variance. When we use N and when we use N-1?
  14. E

    Question about correlation and regression using entire ppopulation

    Hi, I am working on a project were I am doing an analysis on the relationship between two metric variables on a county level in the United States. Since I have the data for all the counties I am doing my analysis on the basis of the entire population(n=3000+). The two variables are however...