normal distribution

  1. T

    Creating standard normal distribution with difference variances within quartiles

    Hi, I have 10,000 data points referring to data on dogs that follow a positively skewed distribution that I have grouped into quartiles. I would a second distribution (highly correlated with the first distribution) associated with the same set of dogs whereby the distribution represents a...
  2. C

    Equivalency testing - CI approach and TOST don't match

    Hey everyone, I'm doing some equivalency testing with both the CI approach and TOST to demostrate the equivalency of two scanning methods. For most of my samples, results align as one would expect, i.e. if the CI lies within the upper and lower bounds, the p-values calculated with two...
  3. T

    parametric or non-parametric in comparison of a dependent variable within several gro

    down vote favorite I am comparing maths and chemistry scores of students in several schools. I am not comparing the schools with each other. I am just trying to say that students do better in maths than in chemistry in all of the schools studied. So I am comparing the maths and chemistry...
  4. Z

    Plotting in r

    Hi There I've goodness of fit my data 2 times. one time for normal distribution and another time for T.distribution. I have about 2500 data and I need to do graphical illustration now. my graphical illustration should be mix of ecdf and cdf for each of them( normal and student t). I'm pretty...
  5. E

    Normal distribution

    Hi all, I'm generating a random normal distribution and i don't control the mu and sigma (its a matlab function that i need to use because the ratio between the numbers). Is there any way to change the mu and sigma and still keep the same ratio between the numbers in the vector? I hope you...
  6. Y

    For the Normal Distribution, why < and <= is the same thing?

    For the Normal Distribution, why is the case that "<" (less than) is the same thing as "<=" (less than or equal to), computationally? That is, why can we summarily disregard the "equality" portion?
  7. J

    Help Building Useful Normal Distribution Calculator

    I want to develop my own Normal Distribution calculator, to provide to a developer to perform a task within an app. I want a user with little knowledge of statistics to be able to perform, and understand Normal Distribution calculations. Here is what I want it to accomplish . . . Given the...
  8. A

    Normal Distribution

    Suppose that in an apartment building run by the Probandstat rental company, the inhabitants's weights follow a normal distribution with mean 73.0 kilos and standard deviation 13.65 kilos. A new elevator must be installed. The elevator company rates the safe carrying capacity of the new...
  9. N

    stuck with this problem!!!! need help

    The minimum force required to break a particular type of cable is normally distributed with mean 12,432 and standard deviation 25. A random sample of 400 cables of this type is selected. Calculate the probability that at least 349 of the selected cables will not break under a force of 12,400...
  10. M

    Determining outliers

    Dear folks, I am interested in statistics but I never had a course in college and I've had to learn a few basic things myself. This time, I am working on something that is beyond my comprehension. I have a set of environmental data (20 soil samples) which I am playing around with. (See below.)...
  11. D

    Comparing a Binomial and Normal Distribution

    So I'm currently analyzing several sets of data, that all represent the exact same type of data. There are multiple sets of this data, but however are in different forms. That is, some of this data is in the binary form, either presence of absence, while others are in the quantitative form. My...
  12. Z

    The effects of transforming skewed data

    Hi There, I would like to know more about transforming data. I know that for parametric statistics data needs to be normally distributed, but I am confused about when this does and does not apply. Doesn't transforming data to make it normally distributed hide any experimental effects you...
  13. C

    Basic help with stats for drug treatments

    Hi there :wave: So I haven't a clue where to start and am hoping someone on here can point me in the right direction. I'm starting to analyse my data from laboratory research but I don't know which test to use. My data is numerical and follows a normal distribution. I have 2 different...
  14. H

    Logistic Regression as Data Transform?

    Hello everyone, new here, glad to be here! I have what might be an unorthodox question. I use the matlab function 'mnrfit' http://www.mathworks.com/help/stats/mnrfit.html to compute a logistic regression model given input data. The matlab function 'mnrval' performs the inverse...
  15. K

    Compensating errors; normal distribution; subset; monte carlo simulation

    Hi all, Please forgive the slightly long winded explanation, I could really do with some help here. I have a computer simulation which contains multiple variables to which I have applied random perturbations in order to simulate the possible error. The random perturbations are in the form...
  16. A

    When does the Normal Distribution arise?

    Hello guys, Studying the multivariate normal distribution (and the univariate one as well), I found in Muirhead (1982) that the normal distribution arises when "the observations themselves can be regarded as sums of independent random vectors or effects". Mi question is if every time...
  17. D

    Normal and non-parametric repeated test data

    Hi All I have done some experimental work and collected data for the conductivity of water with various concentrations of salt. The experiment collected data every 15 mins for 24 hours. Some of the data produced is Normal and other data sets are not normal. Hence I don't know what stats I...
  18. R

    Finding two unknown Z's...

    Hi! I have two problems in which I have to find the unknown Z or X... I've really done well with this section but somehow I just can't remember how to do this and am worried it'll be on the test. Can anyone point me in the right direction/give me the first step? 1. Find Z so that...
  19. K

    if z-value is a negative number, how can i calculate the Probability?

    Hello guys, :) I have an important question I want to ask. I have already searched the web and my statistics book but I can not find the answer :( I stumbled across this problem when preparing for my final from statistics and I can not figure out how we can get P=1 from a z-value=-10.6066...
  20. C

    Finding a UMVUE for variance of normal distribution

    Let Let X_1,X_2,...,X_n be a random sample from a normal distribution with mean \mu and variance \sigma^2 . I showed that (\bar X,S^2) is jointly sufficient for estimating ( \mu , \sigma^2 ) where \bar X is the sample mean and S^2 is the sample variance. Then assuming that (\bar...