normal distribution

  1. T

    Normal Distribution Investment Question

    I have the following scenario and am looking for help: "I have $20, and can invest in one of two options which are independent (A or B). in one year, A can be sold at $X for every $1 that was originally invested, and similarly B can be sold at $Y for every $1. A and B are both normally...
  2. Z

    ANOVA normality test

    Hello, I was wondering, how many assumptions of normal distribution must be violated to conduct a non-parametric test? In my opinion, in my dataset, only one assumption has been violated which is p<0.05. I think the first Q-Q plot looks ok but I am not sure. Also, I don't understand what the...
  3. L

    Accuracy of a transformation of a data set

    Hello, I'm very new to statistics and ran into a problem that I don't know the answer to. I want to do a capability analysis, but my data set is not normally distributed, so I transformed it using the Johnson transform in Minitab. Now I had a normal distribution and very good CP, CPK values...
  4. S

    Deviation with intervals

    I'm having an issue finding a way to distribute numbers in even intervals for any set of given data. With Standard Deviation, it's easy to find 3 even intervals: 1. Over the average + standard deviation 2. Under the average + standard deviation 3. Somewhere in between both. Basically this...
  5. E

    Multiple Linear Regression Assumptions

    Hi guys! I am gonna model multiple linear regression. Do you think that normality of residuals assumption is met according to the P-P plot? Also, consider the homoscadasticity assumption according to the scatter please. I am writing my Bsc. thesis, what should I do if these two assumptions...
  6. K

    Applying One Tail Test to Daily Data to Estimate Monthly Values

    This is my first post in this forum so I apologize that if I am not formatting my question as seasoned forum users. I have sample of daily historical usage data for part numbers at a factory. There are hundreds of part numbers in my data set. I want to use the historical usage to calculate...
  7. S

    CLT Chi squared and negativity

    A variable with the number of degrees of freedom reaching infinity has a distribution coinciding with normal distribution (as CLT). On the other hand, this variable cannot take negative values. How to explain it? Is there an assumption in CLT that it can be used for positive values only?
  8. S

    Finding sample mean for normal distribution

    Hello friends, I require help on the below question on normal distribution. "An e-commerce company tries to settle the customer complaints on refund within 5 days. If a refund is not processed within 5 days, then the company has to provide coupons for Rs.500 to the customer. If the company...
  9. T

    CI from normal distribution using indicator random variables

    Suppose that {X_1,X_2,...,X_n} is a random sample from N(m,1). Let I_i be indicator random variables such that it is 1 if X_i <= 0 and 0 otherwise. Calculate the 95% confidence interval for m. Suppose that sample is large enough.
  10. A

    Z Table Rookie Question

    We've been told to find critical value that corresponds to 80% confidence level. I dropped 10% from each tail since it's symmetric. Am I right in proceeding by finding where 0.90 is in the table to find out the right limit and then minus that to find the left-end point hoping it leaves 80% in...
  11. M

    What is the Confidence interval of this...?

    HI Friends, I've attached excel sheet having 19 records. Can you guys pls help me in finding 95% confidence interval for this. I tried finding it all way, but I'm not getting correct answer. Should t- distribution or Normal distribution be used..? I Thank in advance. Pls help me in finding...
  12. J

    Calculation of overall ranking from mean, SD, and Z score

    Hey everyone, I was hoping someone could help me. Im applying for a job, and am trying to work out my overall ranking in two seperate exams so that I can include this in the application. Could someone please tell me if my calculation is correct? I have attached the file with my calculation...
  13. S

    Extrapolation - Getting info of a population from a sample

    Hello, I'm working on a problem where I have 30% of a full dataset and I have to estimate the generalization error. To be more precise, let's say I have the information of the transactions of the clients of a bank which has 30% of the countries market. I can easily get the mean, standard...
  14. L

    Comparing one normal and one skewed group

    Dear Forum, I have 2 groups for which I need to compare the length of stay (LOS) post-op: a control and a treatment group. My control group has the following descriptive stats: (n=66; Mean = 8.42; Median = 6.00; SD = 7.45; Kurtosis = 17.66; Skewness = 3.81), while my treatment group is as...
  15. R

    Normal Distribution of multiple Std.Dev´s and Means

    Is there a way to calculate the Normal Distribution of a set of multiple Standard Deviations (SD) and Means (µ)? I am afraid I do no have Access to the raw data from which the SD´s and µ´s were calculated. Many thanks in advance
  16. I

    I need a push in the right direction, not sure how to attack the problems..

    Hi :) I am new here on the forum and find it a bit difficult to learn the way to go at different statistics/probability - problems. For the most times I am able to figure it out myself doing some research, but the last two problems has got me stuck for a few days. I would be really thankful for...
  17. A

    Entrance exam cutoff calculation

    Last month I appeared for the phase II of a nationalized bank exam. I would like to know the effect of sample size on the cutoff score. Unlike Phase II, candidates required for Phase III are same for both years. Phase I exam is easier than Phase II. Assume the difficulty level in each phase for...
  18. E

    How to create a subset with a normal distribution

    Hello, I have a presumably easy question for you, but I am a real newbie in statistics, so please be patient. I have a data set containing N values that more or less follows a normal distribution. I need to select N/10 values among them, creating a subset with the same distribution. How can I...
  19. J

    normal distribution

    Hi everyone! I have a question about the answer of question 19a and e. question a: Find the probability that X is greater than 60. Why do they do 0,5 -0,3944 and not 1 - ...? Question e was: the probability is 0,05 that X is in the symmetric interval about the mean between which two numbers...