Recent content by martinl

  1. M

    Statistics for bridges with wooden poles underneath

    Interesting problem. It will require a lot more than 35 sample poles to give you confidence (more than 300), but if it is average you are after, then it would require less.
  2. M

    Likert Type Items - Analysis

    Dear all, Aileen Fink said that we can treat likert type item values (which are ordinal) as if they are continuous data when we analyse them. Could we also apply this principle to descriptive statistics? For example, a question has [strongly disagree, disagree, neutral, agree, strongly...
  3. M

    Dependent t-test with extra information provided

    Oh, I see, now I can clearly see your point. I didn't know that, stats books don't mention that.
  4. M

    Dependent t-test with extra information provided

    Yes, I would conclude there's NO EVIDENCE that there is a difference between before and after measurements. Since 20 is the upper bound of normalcy. So what's the problem?
  5. M

    Dependent t-test with extra information provided

    I was trying to perform a one tailed t-test, with Ho: mu <=20 (given that mu can go up to 20 and still be considered normal). Isn't this correct?
  6. M

    Dependent t-test with extra information provided

    I recalculated it, it is still not significant under Ho: mu <=20. The t-value is negative, but the Critical Value is 1.729 (df=19). So cannot reject Ho. It was 1 tailed.
  7. M

    Dependent t-test with extra information provided

    This image illustrates my calculation. The p value I got from the test is 0.000, and the test is a two tailed test with test value=20. That p value is represented by the far right orange-coloured area. It is a p value from a two tailed test, but I am doing a one tailed test (Ho: mu < 20), so my...
  8. M

    Dependent t-test with extra information provided

    I don't think so, I am doing a one tailed test now, and 0.000 is the probability of getting >20.
  9. M

    Dependent t-test with extra information provided

    Can I calculate like this : The p value from SPSS is <0.001, so half of that will be <0.0005, that's the probability of mean >20. So the probability of mean <=20 is (1 - 0.0005).
  10. M

    Dependent t-test with extra information provided

    Oh, sorry I was wrong. His claim applied to the mean. So you were right. So I did a one tailed test, Ho is "mean difference <20". The SPSS test I used was one sample t test, I set the test value = 20. The resulting p value = 0.000 (see images below). I am wondering: how should I do the rest ...
  11. M

    Dependent t-test with extra information provided

    That would no longer be a paired t-test. What do we do with the paired data? Thank you.
  12. M

    Dependent t-test with extra information provided

    That sounds like a good idea, but his claim applies only to the after measurement, not the mean difference. Would your idea still work?
  13. M

    Dependent t-test with extra information provided

    Dear all, I did a dependent t-test for a medical research, it was comparing before and after measurements. So the dependent t-test should be the right test to use. The after measurements have a wide range. And then the client provided me with another piece of information: "it is very normal...