Upload
tobias-townsend
View
226
Download
0
Tags:
Embed Size (px)
Citation preview
Sampling for Detailed NDIP Inspections
Emma O’KeefeStR 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))
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
A1 X 19 19
A2i Z 51 24
A2ii Z 51 27
A3 Y 31 31
Sampling- Step 2Divide according to school year size• Divide into:• Small (1-15)• Medium (16-49)• Large (50+)
Summary school information No. pupils in school year Total
Small(1-15)
Medium(16-49)
Large(50+)
Year Populatio
n
319 2396 1017 3732
No. of schools
40 84 17 141
Calculate no. of pupils and schools to inspect
Year Size
No. of schools
No. of children
% of Board year
population
Sample required
Small 40 319 8.5 26
Medium 84 2396 64.2 193
Large 17 1017 27.3 82
Total 141 3732 100 301
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
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
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
Sampling Step 3Random numbers 3.4
• Each school class assigned random number
• Sort by random no. column
Calculate no. of pupils to inspect
No. pupils in school year Total
Small(1-15)
Medium(16-49)
Large(50+)
Year Population 319 2396 1017 3732Proportion of year population (%)
8.5 64.2 27.3 100
No. of children required to sample
26 193 82 301
Calculate no. of pupils and schools to inspect
Year Size
No. of school
s
No. of children
% of Board year
population
Sample required
No. selected schools (pupils)
Small 40 319 8.5 26 6 (28)
Medium
84 2396 64.2 193 10 (199)
Large 17 1017 27.3 82 4 (88)
Total 141 3732 100 301 20 (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 /CPP School Year Size Total
Small Medium Large
X 37 561 468 1066
Y 139 1024 419 1582
Z 143 811 130 1084
Total 319 2396 1017 3732
No. pupils to inspect per class size per CHP/CPP to get sample 300
CHP/CPP School year size Total
Small Medium Large
X 10 158 132 300
Y 26 194 80 300
Z 40 224 36 300
Completed sampling for CHPs/CPPs
No. selected schools (pupils)
Year Size X Y Z
Small 3 (11) 2 (27) 9 (44)
Medium 10 (180) 11 (208) 12 (245)
Large 7 (151) 3 (84) 2 (51)
Total 20 (342) 16 (319) 23 (340)
Weighting
• Results need to be weighted for average for NHS Board area
CHP/CPP Sample size
School Yr % inspected
X 300 1066 28
Y 300 1582 19
Z 300 1084 28
Total for NHS Board
900 3732 24
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.
Useful websites
• www.scottishdental.org• www.dundee.ac.uk/dhsru• www.bascd.org• www.glac.ac.uk/departments/
dentalschool
Appendix 1- CHP/CPPs