# random sampling

1. ### Haunted by Cauchy – A medium level problem

Hi Let's suppose X1 and X2 are two Normally distributed variables. [In general, X1 is from N(m1,s1^2) and X2 from N(m2, s2^2) where m1<m2 and s1^2≠s2^2.] However, let’s say, for the sake of starting the discussion, that both are Normally distributed N(1,2^2) and N(2,3^2). One of X1 or X2 is...
2. ### Test & Control File Selection - Help

Hi all I hope all is great with everyone. I'm new on here so sorry to get straight down to my query and hope that someone might be able to point me in the right direction. Thank you. So: I have a prospects direct mail file and I'm testing a new message, (One change). To ensure it’s the...
3. ### Random Sample Generation w/out Knowing P

I'm trying to solve the following issue: I have two decks of cards. One deck of cards has 40 cards and the other deck has 30 cards. The makeup of cards in both decks is unknown to the tester, however, the tester knows that neither deck contains duplicate cards, respectively. The ultimate goal of...
4. ### Random Sampling

I have a dataset of 1000 with the following variables: subjno, hospnm, and bthwt. I need to complete the object below. Objective: • Convert the Excel spreadsheet into a SAS dataset (permanent or temporary) • Write a program to randomly select 3 VLBW, 10 LBW, and 25 normal infants from each...
5. ### Disproportional Sampling for Uneven Case Controls

Hello, I am looking to do a random sampling analysis of a case/control dataset containing 6X as many controls as cases. Therefore, I need to correct for this overabundance of controls (without simply removing the controls) using disproportional sampling. Is switching the # cases and...
6. ### Random sampling from a database with missing values

Hello everyone! I have a real life problem that I would like to have some help with. I'm somewhat familiar with statistics, but for some reason haven't come up with any good solutions to this. My problem is the following: I have a database of patients with varying amounts of variables...
7. ### Comparison of variability of synthetic and real data

Hello, I'm trying to compare a real dataset with a random (synthetic) distribution to determine whether a pattern I see in the data is real or the result of a random distribution or poor sampling. I've been struggling with this problem for weeks and no number of websites or books are...
8. ### Sampling Q - why can't we replace non-responders by randomly selecting new ones?

We are planning a survey of schools to get state estimates of substance use among youth. We are doing a two-stage survey, where the first stage is a PPS random selection of schools, and the second stage is random selection of classrooms (then the students in the classroom are surveyed). We...
9. ### Using Random Number Table.

In a random number table , the random numbers are given as first thousand, second thousand, third thousand, and so on. Every thousand has 25 rows and 1 to 4, 5 to 8 up to 37 to 40 columns. Suppose i have to draw a sample of size 40 from a population of 10000 and I am using the 1 to 5...
10. ### Random sampling - field research in Bihar, India

Dear all, I am currently doing some research in India for my studies and have question relating to sampling? I need to interview people in those villages who have a toilet, and those people only. I would like to know how to randomly select 1 head member (Male or Female) of the households (HH)...
11. ### randomly sample a vector from any distribution (e.g. gamma distribution)

Hi, help is very much appreciated. Thanks in advance!!! rgamma(...) As far as I know with this function (code) one can randomly sample 100 numbers simultanously. Question: is it possible to sample 100 random numbers e.g. from 100 different gamma distributions using only one command...
12. ### 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...
13. ### simple question about sample randomness

Thanks for looking at this. I've been given a sample of data of 105 cars. Our teacher didn't specify whether or not the sample is random, but most of the hypothesis tests I'm to perform require a random sample. I thought I could get around the possible non-randomness of the sample by taking...
14. ### Audit Random Sample Size

Hi all I’m having some difficulty with some sampling work. I’ve searched around for a few days but need a little help. Hopefully someone here will be able to point me in the right direction. The purpose of the sampling is to audit claims that have been entered and to measure the percentage...