sample

  1. S

    Sampling Distribution Problem

    Roll a dice five times. Record the results in Sample 1. Repeat the experiment for Sample 2, 3, and 4. In a live classroom setting, actual survey data is used. In this knowledge check online environment, please use the following data: Sample 1 Sample 2 Sample 3 Sample 4 2 4...
  2. S

    Is this conclusion drawn from sample or population?

    "When asked what they would use if they were marooned on an island with only one choice for a pain reliever, more doctors chose A than B, C or D." Is this conclusion drawn from population or a sample? I am confused here because how do we know if on an island there were all the doctors that...
  3. R

    Is there a way to increase power in my study

    Hi everyone, I'm working on my 'behavioral change' master thesis. My goal is to design an intervention to reduce printing at the workplace in a big organisation. Unfortunaltely i dont get provided with the printing details on a personal level, so my best bet is too see how much a printer...
  4. Z

    Correlation evaluation

    Is there a single statistic which can reflect the different importance between similar correlations, say 0.7, based on different sample sizes such as n=10 and n=1,000?
  5. J

    Commenting on wider population from survey sample

    I am conducting a survey in 9 restaurants, hoping to gather data on our customer demographic profile. The population is equal to the number of covers the restaurant had over the corresponding period in the previous year. This ranges from 4000 to 10000. Across all sites then, I understand that I...
  6. I

    The Unexpected and Thrilling life of Grass - A Statistical Story

    Hi, I'm an aspiring Environmental Scientist and i've recently finished some data collection to do with Common Grassland Species. My hope was to match my findings against a Botany report done several years ago to see the change over time. However i can't figure out which tests to use as most...
  7. L

    Calibration set for PLS regression

    Hello everyone, New to this forum and kind of wondering why I hadn't thought to search for one before tonight... I hope a light at the end of the 'searching literature tunnel'. Briefly, I use PLS regression to model spectroscopic measurements of plant material. That's probably neither here...
  8. N

    Help with errors in a research

    Hi all, I am new to this forum and I am really glad that I found it. Hope I'll be able to offer some help as well. My problem is fairly simple, but I couldn't find the answer anywhere and my attempts were very poor. I am doing analyses on some soil samples and I am getting an analytical...
  9. L

    Sampling issue

    I want to be able to make comparisons between a specifically selected sample (based on ethnicity) and a randomnly selected sample from the general population. Even though the specific ethnicity represents no more than 10-15% of the population, my randomnly selected sample from the general...
  10. 2

    Quick Population / Media Prob question

    This is hopefully a fairly quick conditional probability question for you guys. Imagine a total population of 22MM people and I am running a media campaign against 2MM of those people. Secondarily, a survey company has access to a random sample of 4MM of the 22MM population. Each week...
  11. A

    Sampling distribution of the sample proportion.

    A random sample of 20 students is selected. What is the probability that the sample proportion exceeds 75%, i.e., more than 15 students (out of 20 selected) will agree that that the course is interesting? You may leave your answer as, for example, 1 − 0.88. (As a standard error use 0.8. Also...
  12. T

    Standard Deviation

    You select a random sample of n = 14 families in your neighborhood and find the following family sizes (number of people in the family). 15, 16, 16, 15, 19, 16, 18, 15, 17,16, 15,17,16, 18 I found the mean family size which is 16.4. To find the mean family size, I added up all of the...
  13. M

    How to sample permutation in r without repeating permutations in R

    Hi guys. I was wondering is it possible to create a matrix or a vector of permutations without repeating them. E.g. create a matrix of 4! = 24 permutations. The way I started is: k <- 4 n <- factorial(k) x <- matrix(NA,nrow= n, ncol =k) for (i in 1:n){ x[i,] <- sample(k)...
  14. J

    Logistic Regression

    Hello, I'm currently working on a churn modelling exercise that uses logistic regression. The challenge that i'm facing now is that the model is not returning good results. My hypothesis is that the churn rate in my data set is too small, such that a logistic regression was not able to pick...
  15. M

    When to use which statistics? Is it correct like this?

    I never had statistics in school and I'm not in college yet so I try to teach in to myself now. That's why everything I write now could be plain wrong: - You use hypothesis tests (independent t-test, paired t-test etc) to test a claim about a population mean/population proportion or to test a...
  16. D

    Theoretical Question Operational Data What is Sample and what is population.

    Hi all. I'm working on operational data of clinical operations, attendance, performance and employee performance. I'm trying to use statistical methods to make regressions, correlations and predictions but I don't know if I should use the mean value and variance for the "sample" I have...
  17. M

    Sample based on 2 stratas/variables

    Hello guys, I have a dataset of 90 observations (health center types). I only need 30% of my cases. I have two stratas/variables (I guess): Region and Hospital type. There are 10 US regions and 5 health center types such as family planning, state dept. etc. How can I do this? what would be...
  18. K

    Confidence interval of mean of queue length (M/M/1)

    Goodday, For a simulation course I had to simulate a single server queue with Poisson processes for arrival and departure (M/M/1). Now, this really was not the issue, the issue is where I personally want to add a kind of validity check, which naturally can only be done with statistics. I...
  19. H

    Resampling in R

    Hi I want to generate two sets of random numbers and see how many times the same number appears in both columns. In R I have been using the code length(intersect(sample(1:369, 51, rep=F), sample(1:369,13, rep=F))) I would like to replicate this 1000 times, each time with a new set of random...
  20. A

    Comparison of two treatments (paired and unpaired)

    Hi all! I'm working on my Master thesis and need to make sure I'm not doing it wrong. My research: Are answers to questions a and b significantly different from one another, and why? Questions a and b are answered on a scale from 0 to 10. My data: 153 survey responses, split into 3...