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Conducting the Random Sample SurveyThe 3000 randomly selected households received mailings beginning on September 4, 2025 and data collection forthe survey remained open for eleven weeks. The first mailing was a postcard inviting the household to participate inthe survey online. The next mailing contained a cover letter with instructions, the survey questionnaire, and apostage-paid return envelope. The final mailing was a reminder postcard giving the household one last opportunityto participate in the survey. All mailings included a web link to give residents the opportunity to respond to thesurvey online, as well as QR codes to further encourage participation.About 0.2% of the 3000 mailed invitations were returned because the household address was vacant or the postalservice was unable to deliver the survey as addressed. Of the remaining 2,994 households that received theinvitations to participate, 280 completed the survey, providing an overall response rate of 9%. The response ratewas calculated using AAPOR’s response rate #2 for mailed surveys of unnamed persons.¹It is customary to describe the precision of estimates by a “level of confidence” and accompanying “confidenceinterval” (or margin of error). A traditional level of confidence, and the one used here, is 95%. The 95% confidenceinterval quantifies the sampling error or imprecision of the survey results based on the total number of responsesreceived. This is because some residents’ opinions are relied on to estimate all residents’ opinions. The margin oferror for the Redwood City survey is no greater than plus or minus 5.9 percentage points around any given percentreported for all respondents (280 completed surveys).Conducting the Open Participation SurveyIn addition to the randomly selected “probability sample” of households, a link to an online open-participation surveywas publicized by Redwood City. The open-participation survey was identical to the random sample survey, withtwo small updates; it asked a question to confirm the respondent was a resident of Redwood City and also aquestion about where they heard about the survey.The open-participation survey was open to all city residents and became available on October 2, 2025. The surveyremained open for seven weeks and 290 responses were received. The data presented in the following reportexcludes the open participation survey data, but the online report includes a tab which provides the complete openparticipation results.
<br />Study Limitations
<br />All public opinion research is subject to unmeasured error. While the methodologies employed for this survey were
<br />designed to minimize this error as much as possible, these other sources of potential error should be
<br />acknowledged, and can include non-response error, coverage error, recall bias and social desirability bias.
<br />Non-response error arises when those who were selected to participate in the survey did not do so, and may have
<br />different opinions or experiences that survey responders. For general resident surveys, where the results are meant
<br />to be generalized to the entire adult population living in households, the mailing lists based on the Delivery
<br />Sequence File from the United States Post Office may exclude certain types of housing units, such as those in
<br />multi-family buildings where mail is addressed to a named resident at the address rather than to a specific unit or
<br />where residents only receive their mail at a post office box and the geographic location of a residence cannot be
<br />determined, there may be a coverage error , although for most locations, this is minimal. Respondents may not
<br />perfectly remember their experiences in the past year (such as participation in social or civic events, for example),
<br />and for some survey items, they may answer in ways they think cast their responses in a more favorable light
<br />(recall bias and social desirability bias).
<br />Survey Validity
<br />See the Polco Knowledge Base article on survey validity at https://blog.polco.us/polco-knowledgebase/margin-of-
<br />error-and-confidence-level-in-survey-results
<br />Contact
<br />Redwood City funded this research. Please contact Jennifer Yamaguma of Redwood City at
<br />JYamaguma@redwoodcity.org if you have any questions about the survey.
<br />1. See AAPOR's Standard Definitions for more information at https://aapor.org/standards-and-ethics/standard-definitions/
<br />2. Pasek, J. (2014). ANES Weighting Algorithm. Retrieved from https://surveyinsights.org/wp-content/uploads/2014/07/Full-anesrake-paper.pdf
<br />3. Targets come from the 2020 Census and 2023 American Community Survey
<br />Unweighted Weighted Target ⁴
<br />Age 18-34
<br />35-54
<br />55+
<br />Area 1
<br />2
<br />3
<br />4
<br />5
<br />6
<br />7
<br />Hispanic
<br />origin
<br />No
<br />Yes
<br />Housing
<br />tenure
<br />Own
<br />Rent
<br />Housing type Attached
<br />Detached
<br />Race &
<br />Hispanic ori..
<br />Not white alone
<br />White alone, not Hispanic or Latino
<br />Sex Man
<br />Woman
<br />Sex/age Man 18-34
<br />Man 35-54
<br />Man 55+
<br />Woman 18-34
<br />Woman 35-54
<br />Woman 55+
<br />32%
<br />37%
<br />31%
<br />32%
<br />37%
<br />31%
<br />56%
<br />32%
<br />13%
<br />13%
<br />10%
<br />15%
<br />13%
<br />11%
<br />24%
<br />14%
<br />13%
<br />10%
<br />15%
<br />13%
<br />11%
<br />24%
<br />14%
<br />23%
<br />19%
<br />12%
<br />6%
<br />8%
<br />21%
<br />12%
<br />32%
<br />68%
<br />32%
<br />68%
<br />14%
<br />86%
<br />52%
<br />48%
<br />52%
<br />48%
<br />35%
<br />65%
<br />45%
<br />55%
<br />45%
<br />55%
<br />58%
<br />42%
<br />42%
<br />58%
<br />42%
<br />58%
<br />60%
<br />40%
<br />50%
<br />50%
<br />50%
<br />50%
<br />51%
<br />49%
<br />17%
<br />19%
<br />15%
<br />15%
<br />18%
<br />16%
<br />17%
<br />19%
<br />15%
<br />15%
<br />18%
<br />16%
<br />30%
<br />16%
<br />6%
<br />25%
<br />16%
<br />7%
<br />Analyzing the DataResponses from mailed surveys were entered into an electronic dataset using a “key and verify” method, where allresponses are entered twice and compared to each other. Any discrepancies were resolved in comparison to theoriginal survey form. Range checks as well as other forms of quality control were also performed. Responses fromsurveys completed on Polco were downloaded and merged with the mailed survey responses.The survey datasets were analyzed using all or some of a combination of the Statistical Package for the SocialSciences (SPSS), R, Python, and Tableau.
<br />The demographics of the survey respondents were compared to those found in the 2020 Census and 2023
<br />American Community Survey estimates for adults in Redwood City. The primary objective of weighting survey data
<br />weighting were age, sex, race, Hispanic origin, housing type, housing tenure, and area. No adjustments were made
<br />for design effects. Weights were calculated using an iterative, multiplicative raking model known as the ANES
<br />Weighting Algorithm.² The results of the weighting scheme for the probability sample are presented in the following
<br />table.
<br />Polco aligns demographic labels with those used by the U.S. Census for reporting purposes, when possible. Some
<br />categories (age, race/Hispanic origin, housing type, and length of residency) are combined into smaller subgroups.
<br />MethodsSelecting Survey RecipientsAll households within Redwood City were eligible to participate in the survey. A list of all households within the zipcodes serving Redwood City was purchased from Polco's mailing vendor, based on updated listings from theUnited States Postal Service.Since some of the zip codes that serve Redwood City households may also serve addresses that lie outside of thecommunity, the exact geographic location of each housing unit was compared to community boundaries using themost current municipal boundary file. Addresses located outside of Redwood City boundaries were removed fromthe list of potential households to survey. Each address identified as being within City boundaries was furtheridentified as being within one of the seven areas. From that list, addresses were randomly selected as surveyrecipients, with multi-family housing units sampled at a rate of 5:3 compared to single family housing units.
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