random sample

  1. A

    Random Sampling strategy for multiple populations

    I have the following situation: 6,000 letters created in July 250 staff created the letters Some staff created more letters than others I'm looking to do a quality assurance exercise where we check the quality of a sample of the letters created by the staff. I need some help to understand...
  2. H

    How to estimate population statistics for each category ?

    I have data from a simple random sample having n elements which I’m using to estimate my overall population statistics (mean). My population can be divided into k categories, and I know the composition of my overall population in terms of these categories. As part of my study, I want to estimate...
  3. N


  4. S

    How to extract representative random subsample from large sample?

    Hi! I am new to SPSS and currently looking at data on family firms and non-family firms and their performance - I want to compare the group of family firms (70 firms) with non-family firms (25 000 firms). As you can see, the sample sizes are very different and I want to make them more similar...
  5. E

    Are the Observations in A Random Sample Independent?

    Hi, guys. I am learning the t-test on my own. The assumptions of t-test have been confusing to me. The assumptions included "A random sample is used" and "The random sample is made up of independent observations", so I wondered the observations in a random sample may not be...
  6. S

    compromise between efficiency and accuracy

    Hi! Not sure I post in the right place, but maybe you can help, and some probabilities can be introduced in discussion for the following problem: I have N sensor measurements (N=5000000) and a random sample of size s (s=20) from this set of data. For each measurement is computed a rank...
  7. I

    SPSS- cross validation of cluster analysis

    In SPSS, I conducted Ward’s method of hierarchical cluster analysis based on squared Euclidean distances followed by k-means nonhierarchical clustering. I am now in the process of validating my final cluster solution by using a cross-validation of a random 50% of the sample. I was able to...
  8. N

    Probability and Samples

    A random sample of n=16 is selected from a normal distribution of a mean of 50 and standard deviation of 10 *what is the probability that the sample mean will have a value between 45-55? I am having a hard time figuring out how to even get started and what formula to use to find the...
  9. A

    My professor and I disagree on a test's answer. would love to get a second opinion.

    The question is as follows: " In a certain country: 10% of the families have no children 20% of the families have 1 child 30% of the families have 2 children 40% of the families have 3 children one child is randomly chosen from all the children in the country. X is a random variable whose...
  10. K

    Is a random sample from a random sample a random sample?

    Sorry for the confusing title. I have a population dataset with ~15million records from which I must produce a random sample of 100K records for a survey. There is some processing and filtering that we do to the population (like removing inactive accounts or removing people surveyed in the...
  11. O

    How to guarantee a "full random" selection from a group?

    Hi all, I need to create a full random selection of 5% from a group (>1000000 elements). The only criteria is, that all elements should have the same probability to be selected. The selected 5% will be compared against the full base later on, but there are no predefined attributes/segments...
  12. K

    Simple Random Sample vs Random Sample

    Problem: "A computer company employs 100 software engineers and 100 hardware engineers. The personnel manager randomly selects 20 of the software engineers and 20 of the hardware engineers and questions them about career opportunities within the company. Does this sampling plan result in a...
  13. S

    Generating Random Sample

    I know that R can easily generate random samples for know distributions - normal, exponential, uniform. But how can I generate a random sample from a known probability distribution (that is not listed)? The probability distribution is rather simple: f(x) = 2x^-3 So, how can I generate a...
  14. L

    Random sample - how to get one?

    Hi, I’m doing a research on job satisfaction in lawyers and I would like to use a random sample. My question is: how can I do this? In the whole country we have 7 regional bars and lawyers must be affiliated to one of them. Thank you.