alpha

  1. H

    How to change the alpha level in SPSS?

    I have to do a Mann-Whitney U test in SPSS and it has to be alpha = 0.01, one-tailed. I know the default is 0.05, but I don't know how to change it to 0.01 in SPSS (for Mann-Whitney U test). Is it even possible?
  2. A

    Cronbachs Alpha- Quick question, urgent help needed

    Hi guys, hope you are all doing fine. I have an exam on monday and need to know how to calculate Cronbach's alpha. I know that you have to use the spearman brown formula when you shorten your scale. I can't quite figure out what to do when the scale gets longer. Here is the example...
  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. P

    Using pooled data formula or not?

    The question is: Broken arms can be treated with surgery or splints. In a study with 200 patients, half had surgery and half used splints. In the surgery group, 80 patients showed improvement after 2 months whilst 50 who used splints improved. Is surgery more effective than splints for...
  5. R

    Multiple-testing correction in Moderation analyses

    Hi Everyone! In an exploratory attempt, I ran 35 moderation analyses (both 2-way and 3-way interactions) of which 7 were significant. NOw the reviewer is warning me about false positives and prompting to run some statistical check that would help to identify those. I tried the conservative...
  6. I

    Quick Question on Hypothesis Testing

    Let's say you test hypothesis at alpha=.05, does that mean that 5% of your rejections will be wrong? Is this statement true? If not, can you give an example? I know that alpha= P(type 1 error), which is the probability of rejecting given Null is true. But I still can't tell whether that...
  7. S

    Help needed for upcoming exam: Chi square

    Okay...I have calculated my chi square with an answer of 8.33. No alpha is specified (so Im assuming it would be stated as 0.05). Degrees of freedom is 1 Question 1: How do I know what the p value is from this information question 2: what does 8.33 mean? does this correspond to a p value...
  8. M

    Alpha under .7 in experience sampling data for some measurement moments

    I am facing a problem with my experience sampling data: Some of my alpha (Cronbach) are under .70 for 25 out of 240 measurement moments. Sometime it is when there are less then 20 subjects but sometime not... I am looking for literature to make a decision: delete those measurement...
  9. C

    Krippendorff KALPHA help!?

    Hi, I'm currently undertaking a project which requires content analysis of US print press in order to explore whether international terror events are framed with a glocalized slant. I have defined a coding scheme and decoded my articles. I am using SPSS. However, whenever I run the command I get...
  10. C

    help? hypothesis test selection and execution

    Hi. I am trying to figure this out and I'm not sure if I am doing it right. a) did I select the correct type of hypothesis testing??? b) am I using the numbers in the right place (I have SD for 3.5 for pop and 2.86 for sample. which one is right for my hypothesis and equation?) c) what else am...
  11. D

    Cronbach Alpha for 3-item scale

    I've read that cronbach alphas are also dependent on the number of items, and for a scale meant only for descriptive purposes, what is the acceptable alpha for a 3-item scale? Would, say, .45 suffice?
  12. B

    Different value of Cronbach's alpha with psych and ltm packages and SPSS

    Hi, I'm trying to look at the internal consistency of a questionnaire consisting of 9 binary items. I mainly use SPSS, but am using R to determine McDonald's Omega coefficient using the omega() function in the "psych" package. The main output I get from the omega function is: Alpha...
  13. A

    one-sided confidence intervals

    [b]1. Let X1,...,Xn be iid with cdf Fθ, where Fθ(x) = (x/θ)^β for x in [0, θ]. Here β>0 is a known constant and θ>0 is an unknown parameter. Let X(n)= max (X1,...,Xn). f(x|θ)=nβ(x^(nβ-1))/(θ^(nβ)) when x is in [0, θ]. Part one was to show that P= X(n)/θ is a pivot for θ. Which I did by...
  14. R

    Power calculation in Critiquing Tool

    Hi all I am currently trying to critique some orthopaedic research papers using the Downs and Black (1998) critiquing tool, but I am completely confused by the final question. It asks: “Did the study have sufficient power to detect a clinically important effect where the probability value for...
  15. C

    Required population size

    Have a few problems that I need some help with. It's been a while since I've done stats. Please don't just give the answers but explain how you got them, what formulas used. Thanks!! 1. You want to compare biceps skinfold in patients with Crohn’s disease to the biceps skinfold in healthy...