Observed intra-cluster correlation coefficients in a cluster survey sample of patient encounters in general practice in Australia
<p>Abstract</p> <p>Background</p> <p>Cluster sample study designs are cost effective, however cluster samples violate the simple random sample assumption of independence of observations. Failure to account for the intra-cluster correlation of observations when sampling...
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| Format: | Article |
| Language: | English |
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BMC
2004-12-01
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| Series: | BMC Medical Research Methodology |
| Online Access: | http://www.biomedcentral.com/1471-2288/4/30 |
| _version_ | 1818021610795302912 |
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| author | Chondros Patty Knox Stephanie A |
| author_facet | Chondros Patty Knox Stephanie A |
| author_sort | Chondros Patty |
| collection | DOAJ |
| description | <p>Abstract</p> <p>Background</p> <p>Cluster sample study designs are cost effective, however cluster samples violate the simple random sample assumption of independence of observations. Failure to account for the intra-cluster correlation of observations when sampling through clusters may lead to an under-powered study. Researchers therefore need estimates of intra-cluster correlation for a range of outcomes to calculate sample size. We report intra-cluster correlation coefficients observed within a large-scale cross-sectional study of general practice in Australia, where the general practitioner (GP) was the primary sampling unit and the patient encounter was the unit of inference.</p> <p>Methods</p> <p>Each year the Bettering the Evaluation and Care of Health (BEACH) study recruits a random sample of approximately 1,000 GPs across Australia. Each GP completes details of 100 consecutive patient encounters. Intra-cluster correlation coefficients were estimated for patient demographics, morbidity managed and treatments received. Intra-cluster correlation coefficients were estimated for descriptive outcomes and for associations between outcomes and predictors and were compared across two independent samples of GPs drawn three years apart.</p> <p>Results</p> <p>Between April 1999 and March 2000, a random sample of 1,047 Australian general practitioners recorded details of 104,700 patient encounters. Intra-cluster correlation coefficients for patient demographics ranged from 0.055 for patient sex to 0.451 for language spoken at home. Intra-cluster correlations for morbidity variables ranged from 0.005 for the management of eye problems to 0.059 for management of psychological problems. Intra-cluster correlation for the association between two variables was smaller than the descriptive intra-cluster correlation of each variable. When compared with the April 2002 to March 2003 sample (1,008 GPs) the estimated intra-cluster correlation coefficients were found to be consistent across samples.</p> <p>Conclusions</p> <p>The demonstrated precision and reliability of the estimated intra-cluster correlations indicate that these coefficients will be useful for calculating sample sizes in future general practice surveys that use the GP as the primary sampling unit.</p> |
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| id | doaj.art-d1344944376c4aebbc77b59c26f5c940 |
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| language | English |
| last_indexed | 2024-04-14T08:21:20Z |
| publishDate | 2004-12-01 |
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| spelling | doaj.art-d1344944376c4aebbc77b59c26f5c9402022-12-22T02:04:12ZengBMCBMC Medical Research Methodology1471-22882004-12-01413010.1186/1471-2288-4-30Observed intra-cluster correlation coefficients in a cluster survey sample of patient encounters in general practice in AustraliaChondros PattyKnox Stephanie A<p>Abstract</p> <p>Background</p> <p>Cluster sample study designs are cost effective, however cluster samples violate the simple random sample assumption of independence of observations. Failure to account for the intra-cluster correlation of observations when sampling through clusters may lead to an under-powered study. Researchers therefore need estimates of intra-cluster correlation for a range of outcomes to calculate sample size. We report intra-cluster correlation coefficients observed within a large-scale cross-sectional study of general practice in Australia, where the general practitioner (GP) was the primary sampling unit and the patient encounter was the unit of inference.</p> <p>Methods</p> <p>Each year the Bettering the Evaluation and Care of Health (BEACH) study recruits a random sample of approximately 1,000 GPs across Australia. Each GP completes details of 100 consecutive patient encounters. Intra-cluster correlation coefficients were estimated for patient demographics, morbidity managed and treatments received. Intra-cluster correlation coefficients were estimated for descriptive outcomes and for associations between outcomes and predictors and were compared across two independent samples of GPs drawn three years apart.</p> <p>Results</p> <p>Between April 1999 and March 2000, a random sample of 1,047 Australian general practitioners recorded details of 104,700 patient encounters. Intra-cluster correlation coefficients for patient demographics ranged from 0.055 for patient sex to 0.451 for language spoken at home. Intra-cluster correlations for morbidity variables ranged from 0.005 for the management of eye problems to 0.059 for management of psychological problems. Intra-cluster correlation for the association between two variables was smaller than the descriptive intra-cluster correlation of each variable. When compared with the April 2002 to March 2003 sample (1,008 GPs) the estimated intra-cluster correlation coefficients were found to be consistent across samples.</p> <p>Conclusions</p> <p>The demonstrated precision and reliability of the estimated intra-cluster correlations indicate that these coefficients will be useful for calculating sample sizes in future general practice surveys that use the GP as the primary sampling unit.</p>http://www.biomedcentral.com/1471-2288/4/30 |
| spellingShingle | Chondros Patty Knox Stephanie A Observed intra-cluster correlation coefficients in a cluster survey sample of patient encounters in general practice in Australia BMC Medical Research Methodology |
| title | Observed intra-cluster correlation coefficients in a cluster survey sample of patient encounters in general practice in Australia |
| title_full | Observed intra-cluster correlation coefficients in a cluster survey sample of patient encounters in general practice in Australia |
| title_fullStr | Observed intra-cluster correlation coefficients in a cluster survey sample of patient encounters in general practice in Australia |
| title_full_unstemmed | Observed intra-cluster correlation coefficients in a cluster survey sample of patient encounters in general practice in Australia |
| title_short | Observed intra-cluster correlation coefficients in a cluster survey sample of patient encounters in general practice in Australia |
| title_sort | observed intra cluster correlation coefficients in a cluster survey sample of patient encounters in general practice in australia |
| url | http://www.biomedcentral.com/1471-2288/4/30 |
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