z score

  1. C

    Cohen d and Z scores

    Hi everyone, I should start by saying that I posted the same question that I will expose here on the psychological research forum. However, as I did not receive any answer, I wonder whether I misplaced my post. I apologize if this kind of repetition contravenes any of the rules of Talk...
  2. D

    Help - How do you calculate Z scores given mean and standard deviation?

    I need to calculate z(obs) when given mean and standard deviation from a population and one sample, as in μ0 =32, σ0 =10, m=27, and n=25, assuming H1: μ1 − μ0 < 0. What would I do differently assuming H1: μ1 − μ0 ≠ 0? Thank you for an help provided.
  3. S

    Determining If Difference Score Was Obtained By Chance

    For example lets say a counselor has been using a depression test on clients at the start of treatment and again 6 months later. When the counselor compares the scores how can he/she rule out that the score difference could be obtained by chance at the .05 level? With a test-retest correlation...
  4. K

    Directional test help

    Directional test (H1:M<μ) – In the city there is normally a mean of 75 parking tickets issued per officer with a standard deviation of 12. The police are testing a new no parking signs using a sample area of 30 officers and tickets are down to a mean of 68. Is this significantly lower?
  5. K

    I need help with directional test

    Directional test (H1:M>μ) – You are trying out a new fertilizer on your farm. The population mean for your corn is 130 lbs per acre with a population standard deviation of 20 lbs. Your test sample of 60 acres resulted in 133 lbs per acre. Is this significantly more? The z score i got is...
  6. C

    Can you perform an ANOVA on r-values (correlation values)?

    Hi all: This may be a simple question but... I'm doing neuroimaging research and long story short, I am doing what is essentially a correlational analysis wherein my output is a brain's-worth of r-values (so like 15000 voxels worth of r-values). In this particular study I had 3 groups and I...
  7. J

    Is a Z score of 21.4 a valid value?

    Hi folks, I have a dataset that is highly skewed right. When calculating Z-score, I was expecting to see values up to as high as 6 (6 standard deviations from the mean). In my head, I was thinking that 6 was the highest possible value. I'm pretty certain my calculation is correct, but would...
  8. 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...
  9. R

    Finding the Z-Score for Safety Stock Calculations

    Dear Forum, I want to calculate the safety stocks required by our company to achieve a certain service level for our customers. The basic literature around this topic is quite clear: • Find the Standard Deviation of the Demand (expressed in weeks of demand in my case) • Define the service...
  10. L

    Finding the z score for a hypothesis test

    Help! I'm working on a project that is due at the end of the week and I can't figure out the z score for this hypothesis test. According to the US Census, 38% of college students are over the age of 25. Out of the 60 students randomly surveyed, 20 said that they were over the age of 25, so...
  11. B

    Z-scores with non-normal data

    Hi, I am reviewing someone's study in which they used z-scores to standardize and compare data. I see no mention of their test for normality and when I looked at their raw data, I found much of it to be heavily skewed and not-normally distributed. I need to determine whether this means...
  12. C

    Can someone help me with finding the P-Values for these problems?

    I have a test tomorrow and am not understanding this section very well. I need help on two problems if someone can explain how to do them! Pleaseeee! I have the answers but i want to understand HOW to do them. Obviously i don't expect anyone to do both problems for me. I know that's asking a...
  13. S

    Applying Normal Distribution

    So here is the question followed by what the steps I took to solve it. Please let me know if I have done this correctly: Question: The time needed to complete an exam in a particular college course is normally distributed with a mean of 80 minutes and a standard deviation of 10 minutes...
  14. I

    How to find Z-value given probability?? PLEASE HELP

    Hi, I'm struggling on how to find the z value given the probability (working backwards using the table). Here's an example: The demand for a daily newspaper at a stand is known to be normlly distributed with a mean of 150 and a standard deviation of 25. How many newspaper should the...
  15. T

    Normal distribution, Z-Score and Probability Help.

    I'm having a difficult time trying to answer these questions. Any help would be very helpful. The time it takes a randomly selected job applicant to perform a certain task has a normal distribution with mean 120 seconds and standard deviation 12 seconds. 1. We are interested in computing...