normal distribution

  1. M

    Normal Distribution Question Approach

    Hello everyone, first of all, this has nothing to do with coursework's or homework, I'm currently revising for an exam, so please help me. Following question: Grade point averages of students on a large campus follow a normal distribution with a mean 2.6 and a standard deviation of 0.5...
  2. M

    Two tailed t-test for data sets that do not follow normal distribution?

    Hi there, I'm doing some work comparing two sets of people: those I invited to an event, and those who actually showed up. I am comparing the amount of money they donated to our charity in the past. I have the amounts bucketed into about five categories (i.e., $100-$199, $200-$299, etc.)...
  3. K

    lognormal process time, output rate distribution

    For a project of factory lay out we have given an assembly time of 20 min and stdev of 5 min. distribution type is not given but assumed lognormal (since normal is infeasable because of the possibility of negative assembly times). At what rate do the products exit the assembly station?for...
  4. I

    How to find sample variance given population mean and variance (no specific data)

    Hi, I am working on the following problem:confused:: Population Mean = 1000 Population Std. Dev. = 400 Sample N=25 How many, from the sample of 25, are greater than 1000 if the sample mean is 1100. Can I assume the sample std. dev. is the same as the population? Does anyone know...
  5. 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...
  6. L

    Finding IRQ from standard deviation and normal distribution

    Here's my problem. Any help or insight would be greatly appreciated: A report provided a standard deviation on waiting time to single room occupancy hotels to be 12.9 days. Given that the waiting times follow a Normal distribution, what is the IQR here (single number)? Thanks in advance!!
  7. P

    the third statistics independent with sample mean and variance

    As we know, if X1, X2 ... XN are IID normal distribution, then the mean of the samples and the variance of the samples are independent. My question is, could we use X1, X2 ... XN to construct the third statistics, which independent with the sample mean and variance.