John D Crawford

5 Questions 18 Answers 0 Followers

Questions related from John D Crawford

How to explain a Bernoulli's principle paradox?

Imagine two bodies of fluid separated by a horizontal frictionless, and slightly flexible membrane, with the top body of fluid moving with a finite velocity to, say, the left, while the bottom...

16 April 2021 4,518 5 View

Why in Stata, different outputs from principle-component analysis and P-C factor procedures?

Could someone please explain the difference between the pca (principle component analysis) and pcf (principle component factoring) procedures in Stata? They both assume that there is no...

02 March 2021 5,431 3 View

What is the best way of forming composite cognitive domain scores for longitudinal studies?

In longitudinal studies examining change in cognition over time, commonly outcome measures are composite scores formed by combining a number of individual mental tests. Typical examples are...

28 October 2020 7,189 2 View

Are normality assumptions for Pearson correlations and regression analysis contradictory?

For examining the association between two variables, say X and Y, using the Pearson correlation coefficient, the assumption commonly stated in text books is that both variables need to be normally...

21 October 2020 769 15 View

How do I obtain confidence bands for curves derived from meta-analysis?

We have data from a number of longitudinal studies that include participants’ age and a measure of cognition and carried out analyses to combine these data to examine the longitudinal decline of...

04 January 2017 3,275 2 View