Sampling for Detailed NDIP Inspections

1. Sampling for Detailed NDIP Inspections Emma O’Keefe StR in Dental Public Health Presented at NDIP Coordinators’ Study Day 26th July, 2010 (Updated 2014 in relation to sampling at CPP (Community Planning Partnership Level))

2. Aims & Objectives • To give a working example of how to carry out sampling at Board Level and CHP or CPP level

3. Why? • Consistent • Comparisons • Opportunity to share experiences

4. Why sample? • Resources • Necessary • Random and representative • Sufficient size

5. Sampling protocol • State maintained schools • Minimum sample of 250 per area • Select additional 15-20% • All children in class • Refresh sample each year

6. Sampling- Step 1 Board Area Worked example • Lists from Local Education Dept. • Exclusions • 141 schools • 3732 pupils • 216 classes

8. Example

9. Sampling- Step 2Divide according to school year size • Divide into: • Small (1-15) • Medium (16-49) • Large (50+)

11. Summary school information

12. Calculate no. of pupils and schools to inspect

13. Sampling Step 3Random numbers 3.1 • Generate random numbers (>0 to <1) • Select column to input random no. • Use Σ function (more functions) • Select RAND • Press OK

14. Sampling Step 3Random numbers 3.2 • Will give random no. in top cell • Select that cell • Click on little box bottom right • Click and drag down column • Populate random no. in all cells

15. Sampling Step 3Random numbers 3.3 • To set random number values • Highlight random numbers • Copy column • Paste Special • Select Values option • Random numbers will be held

16. Sampling Step 3Random numbers 3.4 • Each school class assigned random number • Sort by random no. column

18. Calculate no. of pupils to inspect

20. Calculate no. of pupils and schools to inspect

21. Sampling at CHP/CPP Level • Why? • Local comparisons • Local planning • How? • Minimum of 250 per CHP/CPP area • Weighting (carried out by ISD)

22. Sampling protocol • State maintained schools • Minimum sample of 250 per CHP/CPP • Select additional 15-20% • All children in class • Refresh sample each year

23. Sampling- CHP/CPP worked example • Lists from Local Education Dept. • Exclusions • 3 CHP/CPP areas • 141 schools • 3732 pupils • 216 classes

25. CHP/CPP Level • Sort into separate CHPs/CPPs • Sort by school year size • Allocate random numbers • Sort by random numbers • Select classes to inspect

26. CHP/CPP pupils in school year

27. No. pupils to inspect per class size per CHP/CPP to get sample 300

29. Completed sampling for CHPs/CPPs

30. Weighting Results need to be weighted for average for NHS Board area

31. Reference • Pine CM, Pitts NB, Nugent ZJ. BASCD Guidance on Sampling for Surveys of Child Dental Health. Community Dental Health 1997; 14 (Supplement 1):10-17. Found www.bascd.org in policy section under guidance dated Friday 23rd January 2004.

32. Useful websites • www.scottishdental.org • www.dundee.ac.uk/dhsru • www.bascd.org • www.glac.ac.uk/departments/dentalschool

33. Appendix 1- CHP/CPPs