statisics

  1. A

    z test and t test

    I understand that we go for t test in regression , after the data has been normally disributed using z distribution. Need to know why cant we use t - test in all the phases , i mean why is it required that t- test requires that the data is normally distributed.....why t-test can't handle this...
  2. J

    MANOVA or repeated measures anova or ANCOVA?

    Hello! For my thesis I want to compare 3 training groups (2 different types of training and 1 control group) to see the influence on mindfulness-skills and exhaustion level (so 1 IV- type of training- and 2 DV). All the participants get a pre and post test. I'm doing the analysis in SPSS, but...
  3. M

    What is normal curve actually?

    Hi All, I am fairly new to Stats and thus this question. I was going through different materials to learn stats. 1. Somwhere its mentiond that a population, if plotted against frequency on a bar graph can produce a normal curve (e.g popcorn popping, heights of people etc) 2. Whereas somewhere...
  4. A

    confusion on outliers

    I am not able to distinguish the outliers - When to go with std. dev and When do we need to go with Median. My understanding on std. dev. is - if the data is away from mean by more than 2 std dev. we consider that as outlier. Similarly for Median, we say that any data that is not in-between q1...
  5. N

    ANCOVA dilemma

    Hi All, Ive been given this question: Categorise the participants into high stress and low stress groups. Compare the two groups in relation to another psychological variable while controlling for a second variable. The data i have available (which i don't need to use all) is age, gender...
  6. C

    Finding Probability using z-table help

    The question is... Assume that the readings at freezing on a batch of thermometers are normally distributed with a mean of 0°C and a standard deviation of 1.00°C. A single thermometer is randomly selected and tested. Find the probability of obtaining a reading less than -0.976°C. P(Z<-0.976)=...
  7. T

    Please help with the following question

    A firm produces chains. The length of each link is independent of each other and normally distributed. The mean length of a link is 10. 95% of all links have a length between 9 and 11. The total length of each chain is the sum of the lengths of its links. You consider chains with 100 links 2...
  8. O

    Mann-whitney U test??

    What if I have two independent groups. In one of the groups age is normally distributed and in the other group age is not normally distributed. Which test should I use to analyze if there is a significant difference between the groups? Mann-whitney U test assumes both groups are not normally...
  9. K

    A quesion about Percentile

    This really drives me crazy, because i know its simple statistics. According to the World Health Organization (WHO), a child growth of age by weight should be like this : http://www.who.int/childgrowth/standards/tab_wfa_boys_p_0_13.txt you dont have to go into the link, here is a screenshot of...
  10. W

    Normal Distribution

    Assuming that the number of marks scored by a candidate is normally distributed, find the mean and the standard deviation, if the number of first class students(60% or more marks) is 25, the number of failed students(less than 30%marks) is 90 and the total number of candidates appearing for the...
  11. G

    Regression on two explicative variables

    Hello, I am currently doing a thesis which aims to explain returns of stocks in function of the ownerships of some stakeholders. In the Excel attached, I would like to explain the returns in the last column with the two explicative variables ( Venture Capital % Ownership and Hedge Funds %...
  12. S

    A statistic question.

    Provider Charge(Total) Fraud %Fraud Fraud*%Fraud A §§§§§§§1000§§§§§§§600§§§§§0.6§§§§§§360 B §§§§§§§100§§§§§§§§70§§§§§§0.7§§§§§§49 C §§§§§§§10§§§§§§§§§8§§§§§§§0.8§§§§§§6.4 D §§§§§§§1§§§§§§§§§§1§§§§§§§1.0§§§§§§1 Please ignore "§" above. Which provider should be given alert? I am...
  13. C

    Basic questions from newbie

    Hi, I am currently learning ML algorithms and implementing in R. I have a couple basic questions. 1.)Is dimensionality reduction same as feature selection? I know that in R specifying importance=T parameter in randomForest function gives you the important features based on info.gain.I was...
  14. S

    SPSS Help

    Hello everyone, I am a psychology undergraduate who has been set a formative assignment (which means its not worth anything but still has to be done) using SPSS. I was wondering if anyone could help me answer these questions as I am struggling and My lecturer scares me and isn't very nice. I...
  15. L

    Question about type of research

    Hello guys!:) I wonder whether anyone of you who is killing in statistics could give an advice. I am writing my master thesis at the moment. The first part of my research is planned to be focused on the sample of N oilservice firms, in other words, firms in the same industry. What i want...
  16. T

    Help with model Matrix GLM

    Hey guys been browsing the forums for a while, and usually find what I need! This is a tad more specific though so Ive made an account!! I've been puzzled by the form of the model for a while.. The model states that the response depends upon y~smoke + drink +smoke:drink +age:smoke. The model...
  17. B

    Could you please suggest a newbie about publishing Statistics related papers?

    Hello, I am quite new in writing and publishing papers. I have written a few papers, not that tough ones statistically, may be, but well written with properly performed analysis. One paper is on nutritional aspect of the country using a nationally representative data. There I have used a...
  18. M

    How to determine the accuracy of three combined tests

    Hypothetically, I have three tests that can determine if someone has cancer or doesn't have cancer. A True positive would indicate that the person doesn't have cancer. Below is a description of each test. Test 1: TP=.7 , FN = .3 , FP= .1 , TN = .9 , Accuracy = 80% Test 2: TP=.8 , FN = .2 , FP=...
  19. R

    Delta method

    I was wondering if anybody can help me as I've been stuck on this problem for ages and my attempts seem to all be incorrect so far. I have four estimators (W,Χ,Y,,Z) and standard errors for each. How can the standard error of D be cacluated from the following equation, where K, and L are...
  20. G

    One Factor Repeated Measures ANOVA questions

    Hi all, I have conducted a repeated measures ANOVA that has one factor with two levels. I also have a one between-subjects factor that has been taken into account. The results have come back to say that there is a significant difference between the within-subjects factor. My question...