Support #725

Sample sizes nurse visit & blood samples

Added by Lindsay Richards about 7 years ago. Updated almost 7 years ago.

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Dear Understanding Society team,

My colleague and I have recently started working with the nurse and biomarker data from waves 2 and 3, bu have come across an inconsistency in the documentation regarding the sample.

In the document entitled "Waves 2 and 3 Nurse Health Assessment, 2010-2012", the eligible sample sizes (+ reasons for non-eligibility) are given on pages 9 and 10 for the GPS and BHPS components separately. At the end of the flow chart we see that the blood sample was taken from 10,175 respondents in wave 2 and 3,342 in wave 3. The total should therefore be 20,644.

However, in the document "Biomarker User Guide and Glossary" a table of combined sample/ response is provided on page 12. Here the number participating in the nurse visit is 20,700. Note that there are further mismatches in other categories (e.g. no contact, pregnant, ill, died or out of scope).
(This second document also provides the reason for the difference in sample size between the health assessment and blood sample so is useful to us).

Could you clarify which source we should follow, or how we might be able to reconcile these differences?
With best wishes,


Updated by Victoria Nolan almost 7 years ago

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Dear Lindsay,

I'm sorry for the delay in getting back to you.

A couple of things we can point out -

If you add up the number who participated in the nurse health assessment you get 20,706 which is essentially the same as in the Biomarker user guide. The discrepancy in the other numbers is because the health assessment guide gives the numbers who were excluded/not eligible to participate in the health assessment while the biomarker guide gives those who were excluded/not eligible to give blood.

Also, at the bottom of page 9 in the W2 and W3 Nurse Health assessment, there is a note indicating that
the 15591 does not include 56 ineligible observations, thus the numbers are essentially the same in both documents.

If you are in any double over the numbers, please refer to the Biomarker User Guide and Glossary.

Best wishes, Victoria.


Updated by Victoria Nolan almost 7 years ago

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