PONE-D-21-05854

Stratified Random Sampling Methodology for Observing Community Mask Use within Indoor Settings: Results from Louisville, Kentucky during the COVID-19 Pandemic

PLOS ONE

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1. We note that data on the perceived sex of observed people were collected. Throughout the manuscript, please ensure that you consistently refer to observed males and females as "perceived female-presenting" and "perceived male-presenting" and please briefly discuss as a limitation the possibility that some of these perceptions may have been incorrect as no conversations were had with people being observed.

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This study is funded by the Louisville Metro Department of Public Health & Wellness

through the Coronavirus Aid, Relief, and Economic Security Act (the CARES Act).

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“YES

1. Sonali S. Salunkhe: Conceptualization, Methodology, Fieldwork organization, Surveyor, Data curation, Formal analysis, Supervision, Writing the original draft, Reviewing and editing

2. Kelsey White: Conceptualization, Methodology, Fieldwork organization, Surveyor, Data curation, Formal analysis, Supervision, Writing the original draft, Reviewing and editing

3. Emily R. Adkins: Surveyor

4. Julia A. Barclay: Surveyor

5. Emmanuel Ezekekwu: Surveyor

6. Caleb X. He: Surveyor

7. Dylan M. Hurst: Surveyor

8. Martha M. Popescu: Surveyor

9. Devin N Swinney: Surveyor”

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: No

Reviewer #2: No

Reviewer #3: Yes

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The manuscript is well written and brings up an important topic in the current context.

Yet, I have a some comments for consideration by the authors.

1) Are there any results in terms of mask type that could be presented in the results section?

2) Why only up to ten visitors were observed in each PA? And which criteria did the observer use to choose the ten visitors that he/she observed in PAs with more than ten visitors? In other words, how did the observer avoid any bias in selecting the ten visitors he/she observed? It is important to clarify it, as an observer could observe different proportions of unmasked and masked visitors depending simply on the procedures adopted.

3) Was the use of facial mask mandatory throughout the period of observation? I suggest providing this information at some point of the introduction and discussion.

4) What was the proportion of PAs that presented reinforcement signs? And did the existence of these reinforcement signs presented any influence on the use of facial mask?

Reviewer #2: The manuscript "Stratified Random Sampling Methodology for Observing Community Mask Use within Indoor Settings: Results from Louisville, Kentucky during the COVID-19 Pandemic” showed data about the use (prevalence of incorrect use) of masks during the COVID-19 pandemic period at the end of 2020. Previous studies have been suggested low levels of incorrectly used masks because of self-reported procedures. This study presented data that may represent better the “real world” scenario since it used an observational evaluation and not a self-reported procedure. I recommend accepting this manuscript after minor revision. Some comments and suggestions are described below:

## Comments on abstract and title

#1. Although the method is a great part of the manuscript, the information about the incorrect use of masks may be the most relevant news from the study. In this way, I suggest authors change the title for “Prevalence of Unmasked and Improperly Masked in Indoor Public Areas during COVID-19 Pandemic: Data Form Stratified Random Sampling Methodology For Observing Community”.

#2. The abstract is clear and presented the lack of information required in the field specifically solved in this manuscript (prevalence of incorrect use of masks is different from observational studies than self-declaration studies). In the abstract, it was informed that “The average mask use prevalence among observed visitors of the 382 visited public areas was 96%, while the average prevalence of proper use was 86%.”. It may be relevant to inform the total number of subjects observed in these 382 public areas.

## Comments on introduction/background

#3. The authors presented the background and the relevance of the study in the introduction adequately. The authors presented the arguments about the use of an observational procedure instead of a questionary to collected data from subjects about the correct use of masks. However, I recommend showing at least some results about the prevalence of incorrect use of masks from the studies cited in the introduction.

## Comments on methods

#4. For better replicability of this study in other cities and countries, I recommend the author inform the number and profile of the volunteers/observators. Were they students from university? Were they wearing special protection? Were they vaccinated before starting the field procedure? Some of these questions also imply the ethical aspects of the involvement of the volunteers.

#5. What was the period of the day (morning, afternoon…) of the observation. The profile of visitors may be different in the early morning in comparison with the end of the day.

#6. The authors informed that “The fourth and fifth questions asked the surveyor’s to perceive the sex and approximate age-ranges”. There was a previous training procedure to prepare the surveyors to identify the age of the subjects? Is there some limitations fro this identification because of the use of masks?

## Comments on results

#7. The results are clear and well presented. I suggest to authors to first present the “Mask wearing for public areas’ visitors” results (page 14) following by the “Mask wearing for public areas’ staff” (page 15) and after that to present the results described now on page 13.

## ## Comments on discussion

#8. Since the adhesion to health recommendation is influenced by many aspects, from political recommendations procedures, level of understanding of the population, media coverage, self-perception of risk, economic and educational status, I suggest to authors include some aspects in the discussion. It is clear the impact of the position of some governments, mainly in Brazil and USA, on the use of masks. I suggest including this scenario in the manuscript. Also, I suggest reading two references: Taylor S. The psychology of pandemics: Preparing for the next global outbreak of infectious disease. Newcastle upon Tyne: Cambridge Scholars Publishing. Cambridge Sch. 2019. This reference discusses many aspects that may interfere in the adhesion of health recommendations. Some parts of this discussion are also present in the discussion of this paper: Heck et al., Insufficient social distancing may contribute to COVID-19 outbreak: The case of Ijuí city in Brazil. PLoS One. 2021 Feb 17;16(2):e0246520. https://doi.org/10.1371/journal.pone.0246520

I hope that this revision helps the authors to improve the manuscript.

Sincerely,

Reviewer #3: Title: Stratified Random Sampling Methodology for Observing Community Mask Use within Indoor Settings: Results from Louisville, Kentucky during the COVID-19 Pandemic

Summary: The study under review explored a method for measuring the prevalence of mask-wearing and proper mask use in indoor public areas without relying on self-report. A stratified random sample of retail trade stores (public areas) in Louisville was selected and targeted for observation by trained surveyors during December 14−20, 2020. The stratification allowed for investigating mask use behaviour by city district, retail trade group, and public area size. The authors noted a high average mask use prevalence (96%) among observed visitors of the 382 visited public areas, with an average prevalence of proper use of 86%. The authors also noted a high average mask use prevalence (92%) among staff, with unmasked staff being observed in fewer public areas. Observing unmasked and incorrectly masked visitors were more common in smaller public places and food and grocery stores. The majority of the observed unmasked persons were male and middle age adults. The authors suggested a continued need to improve awareness of the effectiveness of appropriate facial mask use, financial resources to provide masks, particularly in low-income areas, and education on correct ways to wear a mask.

General comments: The authors are commended for a well-written manuscript. The arguments for the manuscript under review are timely and original. I believe there are minor concerns and issues with the manuscript in its current form that need to be addressed before being considered for publication. All my comments are included below. I hope you will find them to be constructive and helpful.

Minor Concerns: The primary concerns with the manuscript are presented below:

Introduction. The Introduction section is well-written but relatively short in general. The authors are encouraged to bring out the main points a little more firmly and insert necessary information. The authors are advised, for example, to include a priori research hypotheses with their respective references.

Materials and Methods. The study was conducted for a brief period of 2020 December. Could the study findings, therefore, be similar to other periods? Please comment. Additionally, how was the COVID-19-related scenario (n. of cases and n. of deaths) in the USA and Louisville area during the study? The study's results may, at least in part, depend on the pandemic scenario in the city/country. The authors are, therefore, suggested to take into account this inherent "limitation." The authors are also advised to insert a figure depicting the COVID-19 milestones, which could help the readers.

Is there any explanation/reason to observe 10 visitors in each PA? Please comment

Discussion. Face-covering misclassification could be an inherent limitation of this observational study. As mentioned by the authors, both sex and age could have been misclassified due to surveyor bias. Face-covering misclassification, however, could also occur if the mask was removed immediately before the observation. This potential scenario should, at a minimum, be considered by the authors.

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Reviewer #1: No

Reviewer #2: Yes: Thiago Gomes Heck

Reviewer #3: No

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Prevalence of Unmasked and Improperly Masked Behavior in Indoor Public Areas during the COVID-19 Pandemic: Analysis of a Stratified Random Sample from Louisville, Kentucky

PONE-D-21-05854R1

Dear Dr. Seyed M. Karimi,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

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Kind regards,

Cosme F. Buzzachera, Ph.D.

Academic Editor

PLOS ONE

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The authors have properly address all my questions.

I have no further concerns.

The study results are certainly important in the context we are currently living.

Reviewer #2: The new version of the manuscript answered all the questions asked by all reviewers. The conclusion is straightforward and supported adequately by the methods, results, and discussion. I want to congratulate the authors for the relevant and exciting study that can be applied in different locations worldwide.

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7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: Yes: Thiago Gomes Heck