z-score

  1. S

    Random Sample Generation w/out Knowing P

    I'm trying to solve the following issue: I have two decks of cards. One deck of cards has 40 cards and the other deck has 30 cards. The makeup of cards in both decks is unknown to the tester, however, the tester knows that neither deck contains duplicate cards, respectively. The ultimate goal of...
  2. P

    Z Test with unknown sample size

    How would I conduct a z test when I don't have "n"? The instructor never went over what to do without an "n". It has always been provided. Please help me! The national norm for fifth graders on a standardized test of scientific literacy is 37 (σ = 3). Mrs. Jackson determines that the mean...
  3. H

    How to standardize 3 data sets in SPSS

    Hello, I'm trying to standardize 3 data sets in SPSS to increase the power of my sample to 120 subjects in total. The 3 data sets were all conducted using the same procedure but at different times and the number varies between each of the data sets (Set 1: 50 subjects, Set 2: 34 subjects, Set...
  4. A

    w-score vs. z-score with age/sex covariate

    Hi everyone, I want to predict gray matter (GM) volume in a group of patients based on their degree of cognitive impairment, corrected for age and sex. To have a more ‘disease specific’ measure of cognition, I use cognitive scores in a large group (N=500) of healthy controls (HC) as a...
  5. M

    Is there a difference between z-score and effect size?

    I just started teaching statistics to myself (I never had it in school but will need it when I start University). I have problems with z-scores and effect size. I think that you use a z-score if you want to know how a score compares to the mean or standard derivation. And you use the effect...
  6. P

    The z-scores of the 68-95-99.7 rule aren't matching up with the values in my z-table

    The z-scores from the 68-95-99.7 rule, which are 1, 1.96 (or 2), and 3 according to my textbook, arent matching up with the values i get if i try to find them using the Z-table in the appendix of the textbook. For example, the rule says 95% of the normal distribution falls within 1.96-2 std...
  7. S

    How do you calculate the p-value by hand? Only learned how to do it electronically

    Hello, I am making a Java program that can run a full 1-sample z-test for sample mean and I would like to know how to calculate the p-value by hand once you have the z-statistic. I have learned how to calculate it by looking at the z-table and with a calculator, but for the sake of my program I...
  8. W

    Finding the Target mean?

    Hi, I am taking an online Statistics course, and am having a hard time figuring out how to setup this problem. I would appreciate any help I can get, I am a statistics beginner and want to learn the steps in solving this questions. " San Juan Green Tea is sold in 1/2 liter ( 500 ML) bottles...
  9. I

    Z-Score of Z_Scores... Legitimate Analysis?

    (newbie question...) i have a list of z_Scores for a particular dataset. is it a legitimate to find the z-score of a z-score against a set of z-scores.. so trying to find out how far this particular z-score is compared to a set of z-scores. Anything wrong with this type of analysis? is this...
  10. M

    How to I Calculate the Missing Values?

    IQ-scores are standard-score transformed scores having a mean of 100 and a standard deviation of 15; SAT scores are standard-score transformed scores having a mean of 500 and a standard deviation of 100. In what follows, X refers to a raw score from a distribution with a mean of X and a standard...
  11. S

    Normal Distribution

    I cant figure out how to do this problem: I have 2 sets of means and 2 sets of SD 1sth graders scored a mean of 25 and a sd of 5 5th graders scored a mean of 30 and an sd of 10; assume the distributions are normal How do i figure out what percentage of the first graders scored better...
  12. R

    z-scores

    Dear Forum, I have a question regarding calculating z-scores. suppose I sample 20 people and ask them to rate on a 7-point scale how satisfied they are with X. (imagine that this method is perfectly valid and reliably for the sake of this example...) sample mean = 5.77. Previously I...
  13. K

    I really need help on my homework!

    Theres 2 questions I'm really stuck on. One has three parts and is of course one of those "you can't do the next step until you get the first step" kind of thing.\ 1.A set of reading scores for fourth-grade children has a mean of 25 and a standard deviation of 5. A set of scores for...
  14. S

    Normal Distribution and Grade Cut-offs

    Hello, I tried googling this question, watching how-to videos, and read over the chapter in my textbook several times but I cannot seem to understand how to go about solving this question. The following question applies to a normal distribution of statistics test scores with a mean of 100...
  15. V

    Is this a correct statement regarding a normal distribution?

    Note: this is not homework. I am trying to make sure I understand the differences between percentiles and z-score. Please tell me if the following compare/contrast statements are correct. Thanks, Mike 1. The 95th percentile is the value such that 95% of all observations are below...
  16. S

    Finding z score of skewness and Kurtosis

    Dear all, I'm studying stat from Andy Field's "DISCOVERING STATISTICS USING SPSS" 3rd ed. In chapter 5 (Exploring assumptions) page 138 the writer said "To transform any score to a z-score you simply subtract the mean of the distribution (in this case zero) and then divide by the standard...
  17. A

    reliable results?

    Hi, my name is Dave. I am a recent graduate trying to pass a licensing-exam with the state of California. I think I passed the test (my score=73%), but they use a criterion-referencing method where results are compared to a criterion (their passing score= 75%) rather than to the mean. The idea...
  18. E

    Item difficulty/percentile ranking and z-score

    Hi I am taking a course in psychometrics and am studying for my final exam, which is in two days. I was going over some old exam questions and found one that confuses me: "What is the z-score of an item, which 16% answered correctly" Instinctively, I want to say 1.0. I am then...
  19. A

    Probability without z-score?

    Estimate mean of male students on campus. Standard deviation of the heights of young men is about 2.8 inches. Suppose (unknown to you) the mean height of all male students is 70 inches. a) If you choose one student at random, what is the probability that he is between 69 and 71 inches tall...
  20. S

    Computation of Mean/Average Z-Scores

    Hello, EDIT: I am having trouble uploading my .xls file. I also tried putting the .xls into a .zip but I will always receive an error message. How can I solve this? I am a college student and have just started my first class of statistics. I am quite good at math (taking calculus) but I am...