chi-squared

  1. J

    Determining how similar different sets of data are

    I hope this is in the right spot: I have a dataset of ~15,000 unique, nominal, categorical members. From that dataset, I have ~3,000 samples that are subsets of the overall dataset. Each sample has 100 unique members. A member's inclusion in a sample/subset is binary: either it is fully...
  2. A

    Using Chi Square Test to check the effect of a variable?

    So I am a quite beginner in statistics and I am trying to see whether I am using a statistical method in a correct way or not. I am trying to see the effect of income level towards fraud behavior. So in the so-called population, I have counts for each of the bad/good/new users: BAD: 260 GOOD...
  3. R

    Calculation of expected values for chi-squared test

    Folks I need to work out the probability that a set of survey results occurred by chance, and I intend to use a chi-squared test. However, I haven't studied mathematics formally since I was 16, and I need someone to confirm whether my calculations of expected values are accurate and, if not...
  4. D

    large cell counts - Fisher's Exact vs. chi2

    Hi everyone, I read a while back that chi2 was most accurate for observed cell counts of only between 5-70, but now I can't find that reference. I'm wondering if anyone can point me in the right direction. I have samples of 450-650 and have used Fisher's Exact as a result of having observed...
  5. H

    Estimating Failure Rate: Chi-Square v Poisson

    I understand Poisson distribution is for discrete events and can be used to estimate failure rate to a given confidence level from elapsed time and number of failures (assuming constant failure rate). However, in safety system engineering I routinely see the Chi-squared distribution used...
  6. A

    Which statistical test to use to establish different behaviour between groups?

    Hi, I have got a dataset with a dichotomous groupid variable and many other independent categorical variables. My aim is to find out if subjects in first group behave differently than subjects in second group. So far I have done the cross tabulations between groupid and each categorical...
  7. C

    95% confidence interval for the difference in true proportions for Chi-squared test

    Hello, Apologies if this has been covered, but if so I couldn't find it. Can anyone please tell me how to calculate the 95% confidence interval for the difference in true proportions for Chi-squared test (not for the Odds Ratio). I can work it out manually (I know it should be 0.082 to...
  8. U

    Adjusted Chi-squared test for clustered binary / categorical data

    I'm looking for some assistance in statistical analysis with R (ideally), but also some general stats advice. This follows from a review which identified the need for me to adjust for clustering of relatives within family groups in my data set. I am investigating cardiac phenotypes (I'm a...
  9. D

    How to assess Goodness-of-fit

    I have fitted a set of data points to an exponential decay curve of the equation: y=A+Be^(-t). I wish to assess the quality of fit. Is it OK if I did a chi-squared test using X^2 = sum: (O-E)^2/E and then looked up the critical value?
  10. E

    Determining which data set is most like another

    I am new to this forum - so let me apologize in advance if this is the wrong location. Given a specific multivariate data set, and numerous other data sets, I want to find the one most "like" the original. So, for example (this is dumbed down for the sake of space), which set (B or C) is most...
  11. J

    Is Chi-sqaure the right test for analysing these disease test results?

    Hi All! I have three tests testing for three different strains of the same disease. Unfortunately the tests are not very specific since antibodies (and therefore positive results) to the three strains are common in most populations. If however, there is a true outbreak of the disease, then of...
  12. S

    Uniform distribution question

    Large random samples of size n are taken from a population which follows a uniform distribution with mean 25 and variance of 22. a) What is the expected value of the sample mean? b) Can the Central Limit Theorem be applied in this case? c) The probability that a sample mean is greater than 27...
  13. P

    Sample size - chi-squared vs. normal

    Hi, I apologise if this is the wrong thread. I need to calculate sample sizes, but I'm curious as to why the commonly used Krejcie-Morgan tables use a chi-squared formula rather than a student-t or a normal distribution. I see quite a few other papers that use the latter distributions...
  14. R

    How to compare categorical data for more than 2 groups?

    I'm trying to compare categorical data between 4 groups i.e : smoking history (yes or no) between 4 groups of cancer staging (stage I to IV) Some of the cells has 0 value in it (every person in stage I never smoke, while stage II has 5 smokers, etc) Can I still use Chi-squared test for this...
  15. H

    Using chi-squared test for goodness of fit for different sizes of sample?

    Firstly, apologies if I'm posting this in completely the wrong place. I'm trying to figure out a way to allow for different sized samples when doing a chi-squared test for goodness of fit. The degrees of freedom are always the same (11) as I'm trying to test whether a sample of births are...
  16. C

    Newb Question - Chi-squared - I love numbers but theses stats are tripping me up

    I am look at results of a likert scale and trying to establish statistical significance of the difference in percentage of 'top box' scores. Since the frequency distribution of the likert scale is non-normal I figured categorizing the top box is the best test for this. I am pretty sure I need...
  17. E

    chi-square assumptions with survey data

    Hi guys, I've been asked to run some analyses on some survey data and since it's been a long time since i ran one, I just wanted to check I'm not overlooking some assumptions assoicated with the chi-square test of independence as the text books I've been referring to are quite basic. The...
  18. T

    testing for significant diffs between proportions

    Thanks for stopping by, I have a question about analysing responses from a multiple choice question. I'm looking at a question on what topics people talk discuss most online- there was a list of about 30 topics, and participants were able to pick more than one option. I'm not sure how to...
  19. T

    Comparing variable frequency in groups=help!

    Hi, I am in need of desperate help. I have collected data consisting of frequencies of aggression in a group of chickens according to different conditions. I need to be able to find which condition was the most successful at reducing the amount of aggression recorded. I have a control...