variance

  1. S

    Conceptual Question about Independent/Matched Sample t Test Calculations

    I'm trying to better understand something conceptually, and was hoping if a few users might be able to explain it I could understand it better. For the calculations of a test statistics for an independent sample t test, the mean of sample 2 is subtracted from the mean of sample 1 (then 0 is...
  2. P

    A coefficient to determine Variance

    Hi I am working on a system where temperature stabilises with distance but also increases/ decreases based on month/ hour. Is there a way to tell the model that the variance will decrease with distance? Thanks PYork
  3. P

    urgent help need mean variance

    Hi everybody, If a random variable X is distributed in [0,1], can we say E[x]>var[x]? If yes, can you please give me a reference which is stated that or can you please give me the proof? I would be really thankful if you can help
  4. J

    PISA 2012: Calculating variance explained by ESCS

    Hi there! I was wondering if anyone could help me figure out why I am getting the wrong results! I am using the PISA dataset of 2012 to calculate the variance explained by ESCS (socio-economic status). I followed the steps in the PISA DATA ANALYSES Manuel 2nd edition for SAS: 1...
  5. G

    Basic question- Predicting "the whole from a part"

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  6. B

    Randomized Block ANOVA

    While reading through my lecture notes, I came across a randomized block ANOVA model and some assumptions. What intermediate steps did the authors use to obtain these assumptions (Expectation and Variance) from the given model?
  7. P

    Guidance with a random variable problem needed

    Hello. So I have been trying to solve this problem on my statistics course and I'm having a lot of trouble: "In BME Bioinstrumentation lab, each student is given one transistor to use during one experiment. The probability a student destroys a transistor during this experiment is 0.7. Let...
  8. A

    Matrix Multiplication + Save Result by group

    Bonjour a tous, I'm trying to achieve the following multiplication VAR = W*S*W' w: [n,1] S: [n,n] s: [n,1] I have the following variables in Stata: date W s In my case, S is a square matrix [n,n] with 1 in the diagonal and a constant (per period) "s" in the diagonal. The...
  9. N

    not sure how to interpret variance question

    This is a question I have to do through R - Consider two of the indicators for neurological functioning - the finger wrist tapping (FWT_r, FWT_l) and the plate tapping (X2Plat_r, X2Plat_l), by both left and right hands. For which of these sets of variables would you be inclined to use...
  10. J

    Mathematical intuition for variance

    One explanation to "Why do we square the deviations" is.. "The sum of the square deviations of any set of observations from their mean is the smallest that the sum of squared deviations from any number can possibly be. This is not true of the unsquared distances. So squared deviations point...
  11. T

    Negative ICC values in SPSS

    Hi there, I have run an ICC to assess if scores for 5 dimensions of a quality of life scale have been rated the same by child and their parent. Sample sizes are small (n=14) I ran a two way random model and wanted absolute agreement as I am keen to know about differences with the specific...
  12. C

    Comparing the variance of two samples with differing measurement error

    This is a statistics as applied to astronomy problem - I apologise in advance for my woeful stats knowledge! OK - the problem: For several hundred objects, I have a number of different properties for which I have a measurement & associated measurement error. For example, flux density and...
  13. C

    Joint density distribution and Variance

    Hi everyone! I was wondering if there is a way to calculate the joint distribution of two fully correlated variables, both with known distributions, expected value and variance, without knowing the conditional distribution? If this is not possible, is there a way of finding Var(X,Y) =...
  14. A

    Test the difference between the variance of two proportions

    Hello everyone, How can I test the difference between the variance of two proportions? Best, Ale
  15. A

    How much high/low is the variance if a variable?

    Hello everyone, How can you determine if a variable has a high variance or not? The variance, the standard deviation and the coefficient of variation can take all non negative values. Is a variance of 20 high or low? Thanks for you insights, Ale
  16. S

    Proving variance of b0(hat)

    i have a question asking to prove (attached image): I'm completely stuck and any help would be appreciated. thanks
  17. B

    4th-variance?

    Hello any and all, I am no statistician so does the term "4th-variance" mean anything to someone? I am attempting to replicate the technique found in the publication below. The paper suggests that the 4th-variance is related to the expectation operator. The paper also discusses moment...
  18. S

    Mmsee

    If I am given a random vector X with mean [0 1 -1 2]' and a covariance matrix C= [.1 -.3 .5 .1 ; -.3 1 .1 .2; .5 .1 2 .3 ; .1 .2 .3 .2] how do I find the MMSEE of x1 given x2 = 0 x3 = 0 x4 = 0
  19. V

    standard deviation for an equation

    Hi, I am trying to figure out how to get the standard deviation for two equations. The first one is quite simple; it's just how to find the SD for a part of an average value. I have the SD for an average amount of element in 4 values e.g. average = 118 mg/kg and SD = 48 mg/kg I am...
  20. D

    Qualifying statistical power when confidence intervals are the same?

    I derive two different statistics for characterizing the dispersion in a random variable. One, call it E, is an average of ranges. The other, call it R, is an unbiased estimator of the random variable's parameter. But E is far more popular than R because it's easier to calculate and observe...