3.66 Random digit telephone dialing. An opinion poll in California uses random digit dialing to choose telephone numbers at random. Numbers are selected separately within each California area code. The size of the sample in each area code is proportional to the population living there.
(a) What is the name for this kind of sampling design?
(b) California area codes, in rough order from north to south, are
| 209 | 213 | 310 | 323 | 341 | 369 | 408 | 415 | 424 | 442 |
| 510 | 530 | 559 | 562 | 619 | 626 | 627 | 628 | 650 | 657 |
| 661 | 669 | 707 | 714 | 747 | 752 | 760 | 764 | 805 | 818 |
| 831 | 858 | 909 | 916 | 925 | 935 | 949 | 951 |
Another California survey does not call numbers in all area codes but starts with an SRS of eight area codes. Choose such an SRS. If you use Table B, start at line 132.