74 Matching Annotations
  1. Feb 2024
    1. However, α is unknown and must be estimated.

      Say "Sometimes \alpha is unknown..." Clearly it is not true as written. For instance, later in this chapter you give an example of an attenuated correlation due to a median split on X and the correction factor is 2/sqrt(2*pi). This correction factor is a a known quantity and does not need to be estimated.

    2. Range Restriction

      This seems like a non-standard usage of "range restriction" to me. It is usually used to mean that the instrument is unable to distinguish between differences in the underlying latent construct of interest NOT that the observed range of the measurements is restricted due to a selection effect when choosing the sample.

    1. all the essential equations and code needed to correct for biases in our effect size estimates

      "all" is a strong word here. Maybe back it down a little.

  2. Dec 2023
    1. Applied Example in R

      This section (including the example) doesn't make sense to me. I don't see how you can plausibly derive an appropriate correction her unless you have additional (strong) assumptions such as that misclassifications are random.

    2. It is important to note that for many of the corrections converting the standardized mean difference to a point-biserial correlation is often a necessary step

      Do you have a citation for this? This seems like a roundabout way to get a correction.

    3. converge towards each other.

      only if the misclassification process is uncorrelated with the true scores. For instance, in the extreme, if all the As are classified as Bs and all the Bs are classified as As we get the same difference in observed means but just of opposite signs.

    4. the χ2-statistic

      I assume this is the usual chi-square statistic for independence in contingency tables? In any event, you need to provide a formal definition of the statistic.

    1. T

      Is it usual to correct SMD effect sizes for unreliability. To me it seems more natural to think about the mean difference relative to observed score variance than relative to true score variance.

    2. sample

      If so then the correlation between the reliability and effect size estimate should be accounted for, which the formulas you provide do not do.

    3. into

      In general point-biserial correlations do not behave in the same way as Pearson's r ((https://stats.stackexchange.com/questions/589128/converting-cohens-d-to-pearsons-r-ne-calculated-pearsons-r)), so it is not clear to me that this conversation process will work. Do you have a reference?

      It seems like a lot of work to do that likely depends on lots of assumptions and it is perhaps cleaned to just assume the total reliability applies separately within each group.

    4. same sample

      As noted above, your previous formula for when SMD and reliability are computed on the same sample is wrong, so I don't trust this one either.

    5. over-estimate

      Why? if the groups differ only in the mean then this will not be true. If they differ in terms of true score or error variance then it will be true.

    6. separately

      It seems odd to me to compute these separately, since reliability is a function of observed score variance. There is clearly a strong covariance in the estimates that isn't being dealt with here. See also comment on 1 below.

    7. same sample then the standard error

      Again, this is the correct equation if the reliability is assumed to be known ahead of time (in which case you would not need to pool estimates of it, which points out an inconsistency in your presentation). It is NOT the correct equation if both the reliability and the SMD are estimated on the same sample.

    8. ent.

      For this table to be useful you are likely going to have to define what some of these things are.

      The easier thing would be to just cut the whole table since the sources of measurement error are not relevant for how the corrections are used. Thus, the section/table only serves as a distraction from the main point of the chapter.

    9. measurement error

      which of the two corrections that you describe above are you implementing (i.e. reliability estimates obtained from independent sample or from same sample as observed score correlation

    10. (Bobko and Rieck 1980)

      Equation (5.8) does not appear in Bobko and Rieck. They do provide a similar derivation from which (5,8) can be inferred. However, the Boboko and Rieck version uses n rather than n-1 in the denominators and only considers correcting for unreliability in one variable.

    11. estimated from the same sample

      Looking at the Bobko and Rieck reference, this is the formula when the reliability coefficients are considered to be fixed, known, quantities. It is NOT the SE formula when they are estimated on the same sample as the correlation.

    12. ,

      similar to comments in previous chapters, change the notation. Don't use "se" but rather SE(est), where "est" represents that estimator for which you are providing the standard error.

    13. unbiased estimator of the target quantity,

      But that is not so, because, as you noted last chapter r_xy is biased as estimate of rho_TU and as I noted in my comments on the last chapter the proposed corrections depend on normality.

      Additionally, even if we can ignore the above objections the statement would only be true if the reliability estimates are independent of the observed score correlation estimate.

    14. larger than the If we use the definition of an observed score correlation

      Not sure what you are saying here. Just say "Than the true score variance".

    15. independent and dependent variables

      Since correlations are symmetric (i.e. they do not care which variable is dependent and which is independent) I would avoid the "dependent/independent" language when describing correlations. Instead just talk about the two constructs being correlated

    16. T,

      Adding an "i" subscript here (and ff) would be useful to underscore that every person in the population has a true score and so when you later talk about sigma^2_T it refers to variability across the "i" subscript.

    17. variance components

      This alludes to statistical models that are much more complex than what you have presented so far. If you want the reader to contemplate more complicated variance component models (besides just true score and error variance components) you need to explicitly introduce what those models look like.

      I think this can be fixed by just switching the order of 5.4.2 and 5.4.3

    18. raters

      It is odd that you provide an example involving raters here but then you don't discuss what you call rater/observer specific error until much later in the chapter.

    19. standardized and raw.

      If your example is going to address the distinction between standardized and raw versions of coefficient alpha then your chapter needs to explain the distinction in more detail than what you do here.

    20. If we were to assess someone’s level of extraversion using ratings from their mother, father, friend, and sibling, the average of their combined assessments would yield a more reliable score compared to relying solely on a single evaluator

      Well, unless the ratings were perfectly negatively correlated

    1. unbiased estimate

      Again, are you sure this is true generally. For instance, Hedges' correction to the standardized mean difference results in an unbiased estimator only under normality.

    2. It is independent of all other artifact corrections

      Are you sure this is true generally for all other possible artifact correction? Is so, how can you be sure?

    1. Even in small samples, if ei and a^i are independent of one another (i.e., cov(ei,a^i)=0), then there is approximately no bias.

      Do you have a citation for this claim? It seems to me that it is likely false. I see no reason to believe that the bias of a ratio estimator will be small of the denominator and the numerator are independent.

      Also, per my earlier comment, I'm not even sure I know what it means for e_i and \hat(a_i) to eb independent, since one is an unobserved structural parameter and the other is a sample estimate.

    2. small sample bias (see chapter 4: Small Samples).

      OK, in that case I would wait until next chapter to introduce the R code. There isn't much value in showing someone how to get an answer in R that differs from your hand worked example

    3. However, it is important to note that the bias in non-infinite sample sizes is negligible above a sample size of 10

      This cannot be true in general. It may be true under certain conditions, which should be carefully described before you make the claim.