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

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

Why? Consistent Comparisons Opportunity to share experiences

Why sample? Resources Necessary Random and representative Sufficient size

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

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

Example School + Class CHP or CPP Number in Year Number in Class A1X19 A2iZ5124 A2iiZ5127 A3Y31

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

Summary school information No. pupils in school yearTotal Small (1-15) Medium (16-49) Large (50+) Year Population No. of schools

Calculate no. of pupils and schools to inspect Year SizeNo. of schools No. of children % of Board year population Sample required Small Medium Large Total

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

Sampling Step 3 Random 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

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

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

Calculate no. of pupils to inspect No. pupils in school yearTotal Small (1-15) Medium (16-49) Large (50+) Year Population Proportion of year population (%) No. of children required to sample

Calculate no. of pupils and schools to inspect Year Size No. of schools No. of children % of Board year population Sample required No. selected schools (pupils) Small (28) Medium (199) Large (88) Total (315)

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

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

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

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

CHP/CPP pupils in school year CHP /CPPSchool Year SizeTotal SmallMediumLarge X Y Z Total

No. pupils to inspect per class size per CHP/CPP to get sample 300 CHP/CPPSchool year sizeTotal SmallMediumLarge X Y Z

Completed sampling for CHPs/CPPs No. selected schools (pupils) Year SizeXYZ Small3 (11)2 (27)9 (44) Medium10 (180)11 (208)12 (245) Large7 (151)3 (84)2 (51) Total20 (342)16 (319)23 (340)

Weighting Results need to be weighted for average for NHS Board area CHP/CPPSample size School Yr% inspected X Y Z Total for NHS Board

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

Useful websites hool

Appendix 1- CHP/CPPs