1. N


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    Derivation of random variable for chi-square distribution.

    Hello all, In the chi-square distribution, how is the value of random variable derived. In the textbooks, the random variable is given directly as. 1st equation is for random variable, 2nd value is the test statistic used during inference of variance of a population. Source: Introduction to...
  3. D

    Political Polling: Sample Size and Margin of Error

    Hello, My country have a proportional/majority system. I wonder how can a poll have a margin of error of 2.0%, if all the regional samples used in the poll have a bigger margin of error? - Southwest Region: N~64MM, n=880 and E~3.5%; - Northwest Region: N~39MM, n=553 and E~4.5%; - Central...
  4. 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...
  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. K

    Formula for the Confidence interval?

    Formula for the Confidence interval, assuming for a Sample whose standard deviation is same as Population. I need to know the exact formula. I need to know if there is any square root of n in the denominator. Anyone who knows the formula please share.
  7. A

    Comparing an ecological subsample to population

    I have 2 batches of tree species and abundance data collected for a city. The difference between them is the sampling strategy - one was random unstratified, and the other was stratified and clustered. At a glance the species mixes and relative abundances are fairly similar but i want to test...
  8. A

    How many mothers with shoolkids (scholars, pupils). COFFEE inside

    Hello! INSANE REQUEST: There are 22.681M school age kids in Philippines, how many MOTHERS (or FATHERS) do they have? Knowing that the Fertility rate is 3.569 children per 1 woman of reproductive age. My guess would be: 22.681 / 3.569 = 6.355 mothers have those 22.7M schoolkids. Do...
  9. T

    Reporting participant numbers for meta analysis

    Hi there, I am hoping you may be able to help me with a query I have. I am conducting a meta analysis on Random Control Trials using REVMAN. I have secondary data I am trying to input.I wanted to know whether participants are added up in each condition if there are multiple trials or whether...
  10. G

    standardize by population density

    I have a variable called "number of events" for each state. It is a raw number of event that happened during a specific time frame. I was thinking I could use the population density or weighted population density to standardize the number of events across states. Is this correct? I would divide...
  11. V

    Sample Distribution Probability (unsure if correct answer)

    1. Carlinville, Illinois, has just started an ambitious recycling program. Special trucks collect recyclable products once a week, sorted into barrels of paper, glass, and plastic. The amount of glass recycled per week by a single household is normally distributed with mean 27 pounds and...
  12. C

    What is the population parameter of interest? When the responses are normal?

    The problems said: Students in Stanford are supposed to spend on average 3 hours of time per week for every credit hour they take. Last year, 263 randomly selected seniors were contacted and asked how much total time they spent on their studies over the last week and how many credit hours...
  13. S

    Calculation population size and analysis of a study comparing two outcomes

    Calculation sample size and analysis of a study comparing two outcomes Hi i'm having difficulty finding an answer to this specific problem. I'm preparing a pilot study comparing two medical devices. Each device reads a patient's physiological / laboratory data and provides a...
  14. 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...
  15. 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...
  16. M

    Comparing a sub-population to its overall population?

    Hi there, I am collecting data from a population of about 150 or so, and also from a subpopulation within that of 10-15 which are receiving a specific treatment. I am aiming to compare their scores on the same measure, to see if this population receiving treatment is truly 'special' in some...
  17. A

    Have population, use inferential stats? Non-normal dependent variable, what to do?

    Statistics people! I have two questions for you. I am NOT a statistician so please be nice and answer simply :) Background: We are looking at parental leave in Iceland. We are particularly interested in whether the economic crisis and the resulting changes in parental leave legislation...
  18. D

    What test to determine if 5 years of population data has a trend?

    Hello. I have population data for 5 years for several species of birds and I would like to know whether the populations are growing, staying stable, or decreasing. I am using R. So far, what I have been doing is creating a linear model of the count data (or log of the count data) by year...
  19. F

    historical demographics from Census schedules - how to compare? what test to use?

    I have 1900 Census schedule sheets for several boarding schools. Ive gone through the trouble of transcribing the schedule sheets into a database, recording age, gender, race and place of birth of the students at each of the school. I want to compare each of the schools data to a model that I...
  20. C

    help? hypothesis test selection and execution

    Hi. I am trying to figure this out and I'm not sure if I am doing it right. a) did I select the correct type of hypothesis testing??? b) am I using the numbers in the right place (I have SD for 3.5 for pop and 2.86 for sample. which one is right for my hypothesis and equation?) c) what else am...