Sampling plan in health surveys, city of São Paulo, Brazil, 2015

Alves, Maria Cecilia Goi Porto; Escuder, Maria Mercedes Loureiro; Goldbaum, Moises; Barros, Marilisa Berti de Azevedo; Fisberg, Regina Mara; Cesar, Chester Luiz Galvão

doi:10.11606/S1518-8787.2018052000471

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Sumário

Original Article • Rev. Saúde Pública 52 • 2018 • https://doi.org/10.11606/S1518-8787.2018052000471 copy

Sampling plan in health surveys, city of São Paulo, Brazil, 2015

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

OBJECTIVE

To evaluate the sampling plan of the Health Survey of the City of São Paulo (ISA-Capital 2015) regarding the accuracy of estimates and the conformation of domains of study by the Health Coordinations of the city of São Paulo, Brazil.

METHODS

We have described the population, domains of study, and sampling procedures, including stratification, calculation of sample size, and random selection of sample units, of the Health Survey of the City of São Paulo, 2015. The estimates of proportions were analyzed in relation to precision using the coefficient of variation and the design effect. We considered suitable the coefficients below 30% at the regional level and 20% at the city level and the estimates of the design effect below 1.5. We considered suitable the strategy of establishing the Health Coordinations as domains after verifying that, within the coordinations, the estimates of proportions for the age and sex groups had the minimum acceptable precision. The estimated parameters were related to the subjects of use of services, morbidity, and self-assessment of health.

RESULTS

A total of 150 census tracts were randomly selected, 30 in each Health Coordination, 5,469 households were randomly selected and visited, and 4,043 interviews were conducted. Of the 115 estimates made for the domains of study, 97.4% presented coefficients of variation below 30%, and 82.6% were below 20%. Of the 24 estimates made for the total of the city, 23 presented coefficient of variation below 20%. More than two-thirds of the estimates of the design effect were below 1.5, which was estimated in the sample size calculation, and the design effect was below 2.0 for 88%.

CONCLUSIONS

The ISA-Capital 2015 sample generated estimates at the predicted levels of precision at both the city and regional levels. The decision to establish the regional health coordinations of the city of São Paulo as domains of study was adequate.

DESCRIPTORS
Health Surveys, methods; Stratified Sampling; Cluster Sampling; Sample Size; Data Collection; Statistical Analysis

Coordination	Age (years)/Sex				Total
	12 to 19	20 to 59		60 or more
	12 to 19	Men	Women	60 or more
Block 1 – Population in 2010 (aggregate of urban census tracts)
North	268,489	613,562	684,973	266,052	1,833,076
Central-West	155,753	464,696	518,726	238,299	1,377,474
Southeast	277,068	755,332	848,308	403,229	2,283,937
South	335,585	706,625	784,700	217,103	2,044,013
East	304,317	617,650	682,615	206,808	1,811,390
Total	1,341,212	3,157,865	3,519,322	1,331,491	9,349,890
Block 2 – Sample that would be obtained with proportional sharing by age/sex domain
North	124	285	318	123	850
Central-West	96	287	320	147	850
Southeast	103	281	316	150	850
South	140	294	326	90	850
East	143	290	320	97	850
Total	606	1,436	1,600	608	4,250
Block 3 – Planned sample
North	153	234	261	203	850
Central-West	150	223	249	228	850
Southeast	150	219	246	234	850
South	176	247	275	152	850
East	179	242	267	162	850
Total	808	1,165	1,298	980	4,250
Block 4 – Person/household ratio
North	0.3994	0.9128	1.0191	0.3958	-
Central-West	0.2724	0.8126	0.9071	0.4167	-
Southeast	0.3151	0.8591	0.9649	0.4586	-
South	0.4410	0.9286	1.0312	0.2853	-
East	0.4598	0.9332	1.0313	0.3125	-
Total	-	-	-	-	-
Block 5 – Households required for the planned interviews
North	383	256	256	513	513
Central-West	551	274	275	547	551
Southeast	476	255	255	510	510
South	399	266	267	533	533
East	389	259	259	518	518
Total	2,198	1,311	1,311	2,621	2,625
Block 6 – Households to be randomly selected according to non-response
North	709	475	474	950	950
Central-West	1,020	508	508	1,013	1,020
Southeast	881	472	472	945	944
South	739	493	494	987	987
East	721	480	479	960	959
Total	4,071	2,428	2,428	4,855	4,861
Block 7 – Households required by census tracts
North	23.6	15.8	15.8	31.7	31.7
Central-West	34.0	16.9	16.9	33.8	34.0
Southeast	29.4	15.7	15.7	31.5	31.5
South	24.6	16.4	16.5	32.9	32.9
East	24.0	16.0	16.0	32.0	32.0
Total	27.1	16.2	16.2	32.4	32.4
Block 8 – Inverse of the planned sampling fractions
North	947.61	1415.91	1417.19	707.72
Central-West	560.71	1125.27	1124.95	564.39
Southeast	997.44	1862.46	1862.14	930.53
South	1029.64	1544.85	1540.87	771.29
East	918.05	1378.23	1380.57	689.36

Coordination		Age (years)/sex				Total
		12 to 19	20 to 59		60 or more
		12 to 19	Men	Women	60 or more
Occupied households (among those randomly selected and visited)
	North	660	449	437	791	1,004
	Central-West	989	500	502	924	1,186
	Southeast	949	506	495	889	1,192
	South	760	498	513	900	1,124
	East	647	426	402	732	963
	Total	4,005	2,379	2,349	4,236	5,469
Interviews conducted
	North	161	200	229	187	777
	Central-West	113	135	160	201	609
	Southeast	150	182	231	260	823
	South	244	231	301	199	975
	East	191	205	291	172	859
	Total	859	953	1,212	1,019	4,043
Interviews conducted by tract
	North	5.4	6.7	7.6	6.2	25.9
	Central-West	3.8	4.5	5.3	6.7	20.3
	Southeast	5.0	6.1	7.7	2.0	27.4
	South	8.1	7.7	10.0	6.6	32.5
	East	6.4	6.8	9.7	5.7	28.6
	Total	5.7	6.4	8.1	6.8	27.0

Indicators	Domain	Men					Women
Indicators	Region	n	p	95%CI	cv	deff	n	p	95%CI	cv	deff
Use of a health service in the last 30 days	North	198	20.6	14.2–26.9	15.6	1.246	228	36.3	30.0–42.7	8.9	1.016
	Central-West	135	24.4	17.0–31.8	15.4	1.026	158	35.7	27.0–44.4	12.3	1.319
	Southeast	181	29.9	20.5–39.2	15.8	1.920	231	36.4	29.8–43.0	9.2	1.106
	South	229	18.6	13.6–23.7	13.8	0.990	301	35.6	27.1–44.0	12.0	2.391
	East	205	29.3	21.4–37.3	13.7	1.595	291	39.9	33.3–46.4	8.3	1.320
	Total	948	24.6	21.2–28.0	7.0	2.171	1,209	36.8	33.5–40.1	4.5	1.770
Visit to the dentist in the previous year	North	198	59.6	50.0–69.2	8.2	1.927	228	71.4	66.1–76.6	3.7	0.775
	Central-West	134	70.4	62.3–78.5	5.8	1.062	159	77.0	68.4–85.7	5.7	1.705
	Southeast	182	65.6	57.5–73.8	6.3	1.366	230	70.6	61.9–79.2	6.2	2.114
	South	229	52.2	45.4–59.1	6.6	1.096	300	60.2	53.6–66.8	5.5	1.390
	East	203	58.5	51.3–65.7	6.2	1.094	290	59.8	52.8–66.7	5.9	1.480
	Total	946	60.5	56.8–64.2	3.1	1.373	1,207	66.9	63.6–70.3	2.5	1.551
Excellent or good self-assessment of health	North	199	80.6	74.1–87.1	4.1	1.385	229	64.9	55.8–74.0	7.1	2.118
	Central-West	134	84.7	78.4–91.0	3.8	1.050	160	77.5	71.6–83.4	3.9	0.824
	Southeast	182	81.6	73.7–89.6	4.9	1.965	231	73.5	66.2–80.8	5.0	1.599
	South	229	77.1	71.8–82.3	3.4	0.913	300	65.8	59.2–72.5	5.1	1.505
	East	205	77.4	72.3–82.6	3.3	0.779	291	66.6	61.2–71.9	4.1	0.959
	Total	949	79.9	77.0–82.8	1.8	1.815	1,211	69.1	65.9–72.4	2.4	1.884
Health problem in the last 15 days	North	199	16.4	12.3–20.5	12.7	0.628	229	24.7	19.1–30.2	11.4	0.976
	Midwest	135	15.9	11.2–20.6	15.0	0.567	160	20.1	14.4–25.8	14.4	0.827
	Southeast	182	13.4	8.5–18.2	18.2	0.929	231	26.6	19.8–33.4	12.9	1.395
	South	231	9.5	5.2–13.9	22.9	1.271	301	13.9	8.4–19.4	20.1	1.964
	East	205	21.8	16.5–27.0	12.2	0.848	291	21.0	15.8–26.2	12.5	1.195
	Total	952	15.2	13.0–17.3	7.3	1.281	1,212	21.2	18.6–23.9	6.3	1.615
Hypertension	North	200	13.6	7.0–20.1	24.5	1.882	228	23.3	17.1–29.5	13.4	1.239
	Central-West	134	10.6	4.1–17.1	31.0	1.525	159	11.1	3.8–18.5	33.5	2.233
	Southeast	182	13.8	9.3–18.2	16.4	0.780	231	15.5	10.3–20.6	16.9	1.205
	South	231	14.0	9.9–18.2	15.1	0.861	301	20.5	15.5–25.4	12.2	1.154
	East	204	15.7	10.9–20.6	15.7	0.928	291	18.0	13.1–22.9	13.8	1.206
	Total	951	13.8	11.4–16.1	8.6	1.133	1,210	18.1	15.6–20.6	7.0	1.301
Allergy	North	199	16.8	9.5–24.2	22.1	1.969	228	19.9	13.7–26.1	15.8	1.402
	Central-West	134	15.2	8.2–22.0	23.1	1.275	160	18.5	11.2–25.8	20.0	1.448
	Southeast	181	13.3	8.4–18.4	18.6	0.961	229	17.7	13.1–22.3	13.1	0.842
	South	230	5.3	1.3–8.8	32.3	1.353	300	10.1	5.2–15.0	24.5	2.011
	East	205	14.0	9.9–18.2	14.8	0.732	291	15.6	12.0–19.2	11.8	0.741
	Total	949	12.6	10.1–15.0	9.7	1.281	1,208	16.0	13.7–18.4	7.4	1.246

Indicators	Domain	Adolescents					Older adults
Indicators	Region	n	p	95%CI	cv	deff	n	p	95%CI	cv	deff
Use of a health service in the last 30 days	North	158	24.2	18.2–30.2	12.5	0.782	187	42.5	37.2–47.7	6.3	0.541
	Central-West	112	21.4	11.3–31.5	23.8	1.710	199	39.5	32.6–46.4	8.8	0.999
	Southeast	149	24.5	17.6–31.5	14.4	0.992	260	41.4	32.5–50.3	10.9	2.179
	South	242	19.6	15.1–24.1	11.7	0.804	199	43.7	36.0–51.3	8.8	1.200
	East	189	22.1	16.1–28.1	13.7	1.005	170	37.1	29.5–44.7	10.4	1.078
	Total	850	22.3	19.5–25.1	6.4	0.628	1,015	41.0	37.4–44.5	4.4	0.855
Visit to the dentist in the previous year	North	158	65.5	56.5–74.4	6.9	1.421	178	42.3	33.3–51.4	10.8	1.512
	Central-West	113	79.3	68.9–89.6	6.6	1.863	197	61.1	50.5–71.7	8.8	2.387
	Southeast	150	59.7	50.5–68.9	7.8	1.341	258	47.7	36.3–59.0	12.0	3.380
	South	243	60.5	52.7–68.3	6.5	1.580	196	41.8	32.1–51.5	11.7	1.921
	East	188	57.6	51.1–64.2	5.7	0.832	166	37.7	29.3–46.1	11.3	1.264
	Total	852	62.3	58.5–66.2	3.1	1.345	995	46.4	41.5–51.2	5.3	1.535
Self-assessment of excellent or good health	North	161	87.5	83.5–91.5	2.3	0.608	186	60.2	49.7–70.8	8.9	2.225
	Central-West	113	82.4	75.0–89.8	4.5	1.092	201	74.2	67.0–81.3	4.9	1.367
	Southeast	150	80.3	73.6–86.9	4.2	1.082	260	67.2	60.9–73.4	4.7	1.176
	South	243	84.8	80.2–89.3	2.7	0.999	199	56.8	49.0–64.6	7.0	1.259
	East	191	81.3	74.0–88.6	4.6	1.712	172	52.0	43.5–60.5	8.2	1.256
	Total	858	83.3	80.6–86.1	1.7	0.777	1,018	62.7	59.0–66.5	3.0	0.997
Health problem in the last 15 days	North	161	16.6	10.7–22.4	17.8	1.010	187	24.9	16.9–32.9	16.2	1.622
	Central-West	113	13.2	6.3–20.2	26.4	1.194	201	13.9	8.0–19.8	21.6	1.504
	Southeast	150	19.7	11.4–28.0	21.3	1.656	258	20.4	15.3–25.5	12.7	1.057
	South	243	10.4	4.9–15.9	26.6	2.000	199	26.6	13.7–39.5	24.5	4.303
	East	191	19.5	13.7–25.4	15.1	1.049	172	30.2	22.8–37.7	12.5	1.159
	Total	858	16.03	13.0–19.0	9.42	0.922	1,017	22.9	19.3–26.5	8.0	1.216
Hypertension	North	161	…	…	…	…	187	49.2	41.2–57.2	8.3	1.232
	Central-West	113	…	…	…	…	201	56.7	44.4–69.0	11.0	3.168
	Southeast	149	…	…	…	…	259	62.3	55.8–68.7	5.2	1.159
	South	242	…	…	…	…	199	46.8	38.2–55.4	9.3	1.509
	East	191	…	…	…	…	171	55.2	50.1–60.4	4.7	0.465
	Total	856	1.14	0.3–2.0	37.33	1.371	1,017	54.8	51.0–58.7	3.5	1.525
Allergy	North	161	25.6	19.3–31.9	12.5	0.869	187	14.0	8.9–19.1	18.4	1.028
	Central-West	113	24.4	12.1–36.6	25.5	2.373	201	23.5	14.6–32.4	19.2	2.258
	Southeast	149	18.5	9.7–27.3	24.0	1.958	260	17.3	12.5–22.1	14.0	1.065
	South	244	8.9	4.2–13.6	26.7	1.704	198	8.9	4.2–13.7	27.0	1.407
	East	191	25.9	20.0–31.9	11.6	0.901	171	20.4	13.8–27.0	16.3	1.154
	Total	858	19.8	16.6–23.0	8.3	1.439	1,017	16.8	14.0–19.6	8.4	1.455

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[1] Correspondence: Maria Cecilia Goi Porto Alves, Rua Santo Antônio, 590, 01314-000 São Paulo, SP, Brazil E-mail: ceciliagoi2@gmail.com