April 2017 Winthrop Poll South Carolina
This is a
General Population poll of 878 SC residents. Results which use All Respondents have a margin of error of approximately
+/- 3.3% at the 95%
confidence level. Results for Whites
have a margin of error of approximately +/- 4.1%; results for Blacks have a margin of error of
approximately +/- 6.5%; results for GOP & Independent who Lean Toward the GOP respondents have a margin of error of approximately +/- 5.2%; results
for Democratic & Independent who Lean Toward the Democratic Party respondents have a margin
of error of approximately +/- 5.4% -- all at the 95% confidence level.
Any subset will have a larger margin of error. Margins of error are based on
weighted sample size.
Phone calls were made during weekday evenings, all day Saturday, and Sunday
afternoon and evening. Weekday daytime calls are not made to avoid oversampling
those who are more likely to be at home during the day (e.g. retirees,
stay-at-home-parents, etc.). Conducting weekend calls is important to avoid
systematically excluding certain populations (such as those who may work 2nd or
3rd shift during the week). This poll was in the field from April 2 – 11,
survey used (1) Random
Digit Dialing (RDD) and (2) Wireless phone number
sampling. Both RDD and wireless samples are crucial to ensure no adult in
the geographical area of interest is systematically excluded from the
sample. All samples were
purchased from Survey Sampling International (SSI).
weighted based on age, sex, and race using Census Bureau data.
numbers selected for the survey were re-dialed up to six times in an attempt to
reach a respondent. Once a household was reached, we also employed
procedures to randomize within households for RDD
sample. Surveys were conducted in English.
Computerized autodialers were not used in order
to ensure the survey of wireless phones complied with the Telephone Consumers
Protection Act and all FCC rules regarding contacting wireless
telephones. 60% of the
completions came from the wireless sample.
The Winthrop Poll is paid for by Winthrop
University with additional support from The West Forum on Politics and Policy
at Winthrop University.
Additional Explanation of RDD Methodology : (with
descriptions taken from SSI website)
Samples are generated using a database of "working
blocks." A block (also known as a 100-bank or a bank) is a set of 100
contiguous numbers identified by the first two digits of the last four digits
of a telephone number. For example, in the telephone number 203-567-7200,
"72" is the block. A block is termed to be working if some specified
number of listed telephone numbers are found in that block.
Samples of random numbers distributed across all eligible blocks in
proportion to their density of listed telephone households are selected. All
blocks within a county are organized in ascending order by area code, exchange,
and block number. Once the quota has been allocated to all counties in the
frame, a sampling interval is calculated by summing the number of listed
residential numbers in eligible blocks within the county and dividing that sum
by the number of sampling points assigned to the county. From a random start
between zero and the sampling interval, blocks are systematically selected in
proportion to their density of listed households. Once a block has been
selected, a two-digit number is systematically selected in the range 00-99 and
is appended to the exchange and block to form a 10-digit telephone number.