Safer Bars: A Cluster-Randomized Effectiveness Evaluation of Alcohol-related Sexual Violence Prevention Through Bar Staff Bystander Training
Phase: NA
Conditions: Sexual Assault Precursor Behavior
Sponsor: Mary Koss

Evaluation of the Safer Bars Prevention Program for Sexual Assault 
 
NCT: 04141839 
 
Date: March 13, 2025 
 

 
Study Protocol and Statistical Analysis Plan 
Study Protocol 
The objectives of the protocol are to conduct a cluster-randomized controlled trial with 
crossover, multiple sources of data, and a theory-driven analysis plan to assess the immediate 
and intermediate effectiveness of Safer Bars, a primary perpetration prevention program to train 
bar staff to recognize and respond to sexual aggression and its precursors among patrons.  
This prospective evaluation will assess individual-level outcomes, including changes in bar staff 
members’ attitudes, perceived social norms, perceived behavioral control, behavioral intent, and 
subsequent bystander behavior. Bar-level outcomes will include changes in the physical bar 
environment and risk management safety policies. Additionally, we will use GIS mapping to 
identify “hot spots” of liquor licenses in areas within a 3-mile radius of the three major Arizona 
universities and map police dispatches for reports of sexually-violent behavior in these areas 
prior and subsequent to the intervention in order to assess community-level outcomes. 
 
Recruitment. The study will recruit approximately 56 bars with an average of ten 
participants per bar for an intended sample size of 564 individual bar staff and 56 bar 
owners/managers. Sampling of bars will be proportional to the size of student enrollment at 
each of the universities. The study will sample from bars that are located within 3 miles of the 
university campuses, have a current liquor license to serve on-premises, and have not received 
the Safer Bars training within the past year.  
Project staff will generate a list of bars in the catchment areas and will contact their 
owner/managers through combinations of email, phone, social media, and in-person visits. If a 
bar owner/manager is interested in receiving more information, staff will describe the training 
and study, as well as provide informational material. If a bar agrees to participate, the 
owner/manager will sign the Bar Agreement Form, which details the time commitment and study 
details. Project staff will then utilize a block randomization procedure to determine which arm 
(control or intervention) the bar is in and will convey this to the owner/manager as well as details 
about the monetary incentive ($250) available to cover some of the costs of hosting the study at 
their establishment. Research staff may also recruit through organizations or associations 
related to bartending, bartenders, or bar owner/managers within the specified catchment areas. 
Bars may receive Safer Bars training without participating in the study.  
Before training session 1 (intervention group) or the information session (control group), 
research staff will meet with the bar owner/manager to review the consent form and screening 
questions. If the bar owner/manager is eligible and agrees to participate, they will provide 
informed consent and their contact information. At the beginning of training session 1 
(intervention group) or the information session (control group), staff will discuss the study with 
the bar staff, provide them the opportunity to ask questions, assess eligibility, and obtain 
informed consent and contact information. Individuals who do not wish to participate in the study 
may still attend the training. 
Retention. We will take multiple steps to retain participants throughout the project. First, we will 
make participation as convenient as possible by using in-person data collection for the baseline 
surveys and online data collection for the follow-up surveys. Second, we will give reminders to 
participants regarding survey completion. Finally, we will structure our payment and incentive 
schedule to encourage full completion.  
 

Study Design. A 6-month, cluster-randomized controlled trial study design will be implemented. 
Bars (n = 56 bars; n = 564 bar staff; n = 56 bar owners/managers) will be randomized to receive 
either the Safer Bars bystander promotion intervention or will be assigned to a waitlist control 
condition in which they receive the Safer Bars intervention after a 3-month waiting period. 
Participants working at bars in the intervention group will receive two, 2.5-hour in-person 
intervention sessions spaced approximately two weeks apart coupled with assessments pre-
intervention session 1 (baseline) and immediately post-intervention session 2. They will then 
complete follow-up assessments at 3 months and 6 months post-intervention. Participants 
working at bars assigned to the waitlist control group will complete an initial information session 
about the study in which they respond to the same baseline measures as the intervention group, 
followed by a 3-month assessment identical to that of the intervention group. Control bars will 
then be eligible to receive the Safer Bars intervention.  
 
Statistical Analysis Plan 
 
Individual-level Analyses   
Because randomization to study arm will be at the bar level, we will use analytic 
techniques (generalized linear mixed models [GLMMs] and multilevel structural equation models 
[MSEMs]) that account for clustering of individuals nested within bars and repeated measures 
within individuals and allow for participant-level missing data [18,19,20]. Selection of model link 
functions (e.g., identity, log, logit) and error distributions (e.g., normal, Poisson, binomial) in 
GLMMs and MSEMs will be guided by the scale of measurement and observed distribution of 
the outcome measure. To test program effects on bystander behavior, we will estimate GLMMs 
predicting bystander behaviors at follow-up, adjusting for baseline bystander behavior as well as 
any relevant covariates identified in preliminary analyses. GLMMs will include random 
components for bar-level intercepts. To address mediation of program effects via TPB 
constructs, we will estimate prospective MSEMs in which the effect of study arm on bystander 
behavior is mediated through its effects on TPB constructs. Point estimates of indirect effects 
will be computed using a product-of-coefficients approach [21]. As MPlus does not produce 
bootstrap standard errors for indirect effects in multilevel SEMs, Bayesian credible intervals will 
used for inference. To address potential moderation of program effects by participant 
characteristics (gender identity, job position, education, personal sexual assault experiences, 
prior education in sexual assault prevention) and bar characteristics (policies, physical 
environment), we will extend above GLMMs by including Study Arm x Characteristic interaction 
terms. Each significant interaction will be probed to characterize the pattern of differential 
program effects across categories or levels of a background characteristic [22].  
Bar-level Analyses  
Within a generalized linear modeling framework, a series of ANCOVAs will be conducted 
to examine the effect of intervention condition on changes in physical environment 
characteristics and risk management safety policies. Outcome scores at 3-month follow-up will 
be predicted from study arm, adjusting for baseline scores and relevant bar-level covariates. 
The Sidak procedure will be used to control study-wise Type 1 error inflation. 
Community-level Analyses 
 Violent crime datasets will be obtained from relevant municipal police departments via 
public records requests for years prior to and during the study. Maps will be generated using 
ArcGIS ArcMap. Violent crimes of interest will be mapped using the “Esri World Geocoder” 
under the “Geocode Addresses” tool and then shapefile layers will be created.  
Next, spatial information of the liquor licenses for the relevant bars will be obtained from 
the Arizona Department of Liquor Licenses and Control (DLLC) website. Only “on-premises” 
liquor license addresses will be queried and mapped. Shapefile layers of bar locations will be 
created and added to the maps. Utilizing the “Kernel Density” tool within the “Spatial Analyst 

Toolbox” via ArcMaps, bar location density will be mapped against the crime points. The results 
will illustrate the amount of violent crime in a specific location in relation to the density of bars for 
that exact location. Analyses will compare the frequency of violent crime-related police 
dispatches to study catchment areas before and after receiving Safer Bars training. 
 
Power Analysis 
The sample size of 564 individual bar staff (approximately 56 bars [28 bars in each study arm] x 
average of 10 participants per bar) affords power of .80 to detect small-to-moderate 
standardized between-group differences (i.e., intervention effects) on individual-level outcomes 
ranging from d = 0.28 to 0.45, depending on an assumed intraclass correlation (ICC) of .10 for 
outcome scores, assumed correlations between baseline and follow-up scores ranging from r = 
.10 to .50, and assumed ICCs for pre-post change scores ranging from .05 to .10. Adjusting for 
bar-level clustering, the proposed sample should afford power of .80 to detect indirect effects 
and small-to-moderate constituent direct effects (ds= 0.35-0.45 for X to M, r2s = .04-.09 for M to 
Y), assuming a 10% attrition rate. For bar-level outcomes, the proposed sample size affords 
power to detect large effects (ds = 0.66-0.76, for pre-post correlations of r = .10-.50).