to contain approxinately the sanie nanber 

 of households in each. 



Each of the seventy strata was then 

 divided into a number of small area seg- 

 ments having boundaries which could easily 

 be identified in the field by the inter- 

 viewers, ^ach such trea segment contained 

 one or more clusters of households or san- 

 plijng units. The number of sampling ■anits 

 or interviev;er work loads assigned to each 

 area segment iras based on data available on 

 the number of occupied divelling units lo- 

 cated within these segment boundaries. 

 These data vjere obtained from a variety of 

 sources including 1950 block statistics, 

 1930 enumeration district statistics, state 

 highway maps, etc. 



The geographic strata in each city 

 were all constructed to contain the same 

 number of sampling units with the exception 

 of Detroit. In the central city port.ion cf 

 Detroit , the area strata for the tracts in 

 the white zone (that is, the tracts with at 

 least 90 percent of their 1950 dvjelling 

 units occupied by white families) were con- 

 structed to contain twice as many sampling 

 units as the remaining area strata estab- 

 lished for the Detroit urbanized area 

 sample. Initially, tv;o sampling units were 

 selected with equal probability and without 

 replacement from each of the geographic 

 strata, yielding a sample total of IhO 

 sampling units for each urbanized area. 



The sample selection was accomplished 

 hy choosing tv;o random numbers for ujich 

 stratum between one and the total number of 

 sampling units in the stratum. Thus, the 

 sampling rate v;as the same for all geo- 

 graphic strata within a city with the ex- 

 ception of those comprising the white zone 

 in Detroit referred to above. Sinco these 

 strata contained twice as many sampli:ig 

 units as the remaining geographic strata 

 in Detroit they viere sampled at one -half 

 the rate of the remaining strata in that 

 urbanized area. The disproportionate sam- 

 pling in Detroit was deemed necessary to 

 yield sufficient intervie'ws with non-^'ihite 

 families for separate tabulation. 



The number of strata and sampling 

 units for the central cities and the re- 

 maining portions of the three urban j.zed 

 areas are shown in the follav;ing table: 



Append.ix Table 1 



NUMBER OF STRATA AND SMPLHIG UNITS OF 



URBANIZ?:D AREAS EXCLUDED IN THE 



MOriVATIOH SUiT?.'EY 



The decision to include a sample of 

 non-white households in Orangeburg, South 

 Carolina was made after the sample for the 

 three principal urbanized areas was de- 

 signed and selected. The expected sample 

 size in each of the three urbanized areas 

 was then reduced from 3uO households to 

 725 households in order to shift a portion 

 of the field budget to the survey to be 

 conducted in Orangeburg County. Rather 

 than design and select a new sample in 

 each of the three urbanized areas, twenty 

 sampling units in Birmingham, thirteen in 

 Boston, and twenty-eight in Detroit were 

 discarded at random with a condition that 

 no more than one sampling unit would be 

 discarded from any one stratum. 



Strict field procedures were employed 

 to detenriine the eligible households 

 associated with the selected sampling units 

 in an unbiased manner. The interviewers 

 were required to list the occupied dwelling 

 units in each area segment containing a 

 selected sampling unit in advance of the 

 interviewing. The listings shov;ed addresses 

 and other necessary identification for all 

 dwelling units located within the boundaries 

 of each area segment. The enumerators were 

 provided with maps showing these boundaries, 

 as well as the starting point and direction 

 to take through the sejTnent for listing 



