Three vaping prevention video ads from the FDA's The Real Cost prevention campaign about vaping addiction will be shown to participants at week 0, 1, and 2. Ads will be shown in a random order.

Three neutral (i.e., purely informational and without graphics) vaping video ads developed by the Investigators will be shown to participants at weeks 0, 1, and 2. Ads will be shown in a random order.

The 3-item Mean Cognitive Elaboration Scale assesses the extent to which participants have thought about the addictiveness or harmfulness of vaping over the past 7 days. Response options range from 1 to 5. The overall scale score is calculated by averaging the three items, with scores ranging from a minimum of 1 to a maximum of 5. Higher scores indicate greater cognitive elaboration, suggesting a more effective engagement with the content (a better outcome).

The 3-item Mean Social Interactions Scale assesses the extent to which a participant has discussed the addictiveness or harmfulness of vaping with others in the past 7 days. Response options range from 1 (0 times) to 6 (11 or more times). The overall scale score is calculated by averaging the three items, resulting in a score range from a minimum of 1 to a maximum of 6. Higher scores indicate more frequent social interactions, which are considered a better outcome.

The 3-item Vaping Health Harm Risk Beliefs Scale assesses the extent to which participants believe that vaping will lead to health harms. Response options range from 1 to 5. The overall scale score is calculated by averaging the three items, with possible scores ranging from a minimum of 1 to a maximum of 5. Higher scores indicate stronger beliefs in the health risks associated with vaping, which is considered a better outcome.

The 3-item Vaping Addiction Risk Beliefs Scale assesses the extent to which participants believe that vaping will lead to addiction. Response options range from 1 to 5. The overall scale score is calculated by averaging the three items, with a score range from 1 to 5. Higher scores indicate stronger beliefs in the risk of addiction due to vaping, which is considered a better outcome.

The 3-item Vaping Attitudes Scale assesses a participant's attitude towards vaping (e.g., good/bad). Response options range from 1 to 5. The overall scale score is calculated by averaging the three items, with scores ranging from 1 to 5. Higher scores indicate a more positive attitude toward vaping, which is considered a less desirable outcome (i.e., worse outcome).

Participants will be asked to report the number of days they vaped over the past 21 days. We chose to retain the continuous measure of the number of days spent vaping rather than dichotomizing this outcome, due to the substantial variability observed in the number of days e-cigarettes were used. A higher value indicates more days that participants vaped, which is considered a less desirable outcome (i.e., worse outcome).

The 1-item Mean Smoking Health Harm Risk Belief Measure assesses the extent to which a participant believes that smoking will lead to health harms. Response options range from 1 to 5, with higher scores indicating stronger beliefs in the health risks associated with smoking, which is considered a desirable outcome (i.e., better outcome).

The 1-item mean smoking health harm risk belief measure assesses the extent to which a participant believes that smoking will lead to health harms. Response options are on a 1 to 5 scale, with higher scores representing a stronger health harm beliefs about smoking, which is a desirable outcome (i.e., better outcome).

The 1-item mean smoking attitude measure assesses a participant's attitude toward smoking (i.e., good/bad). Response options are on a 1 to 5 scale, with higher scores representing a more positive attitude toward smoking, which is considered as less desirable outcome (i.e., worse outcome).

The 3-item Mean Susceptibility to Smoking Cigarettes Scale assesses a participant's susceptibility to smoking cigarettes. Response options range from 1 to 5. The overall scale score is calculated by averaging the three items, with possible scores ranging from 1 to 5. Higher scores indicate a stronger susceptibility to smoking, which is considered a less desirable outcome (i.e., worse outcome).

Participants will be asked to report the number of days they smoked cigarettes over the past 21 days. We chose to retain the continuous measure of the number of days smoking rather than dichotomizing this outcome, due to the substantial variability observed in the number of days cigarettes were used. A higher value indicates more days that participants smoked cigarettes, which is considered a less desirable outcome (i.e., worse outcome).

The 6-item FDA Mean Perceived Message Effectiveness Scale evaluates a participant's overall impressions of an advertisement. Responses are provided on a scale from 1 to 5. The overall scale score is calculated by averaging these six items, resulting in a possible range of 1 to 5. Higher scores indicate that participants found the advertisements to be more informative (i.e., better outcome).

The 3-item Avoidance Scale measures the degree to which a participant wishes to avoid engaging with an advertisement. Responses are provided on a scale from 1 to 5. The overall score is calculated by summing the scores of the three items and then dividing by 3, resulting in a possible range of 1 to 5. Higher scores indicate greater avoidance, which is considered a less desirable outcome (i.e., worse outcome).

The 1-item reactance measure evaluates the degree to which an ad annoys participants, using a response scale from 1 to 5. Higher scores indicate greater reactance to the ad, representing a less favorable outcome.

The 3-item Mean Vaping Social Enhancement Beliefs Scale measures participants' perceptions of the social benefits of vaping, such as fitting in better with friends. Responses are on a 1 to 5 scale, with overall scores calculated by averaging the three items. Scores range from 1 to 5, where higher scores indicate a stronger belief in the social benefits of vaping, a less desirable outcome (i.e., worse outcome).

The 3-item Mean Vaping Affect Regulation Beliefs Scale evaluates participants' beliefs about the experiential benefits of vaping, such as feeling good. Responses are recorded on a 1 to 5 scale. The overall score, which also ranges from 1 to 5, is calculated by averaging the three items. Higher scores indicate that participants expect more significant emotional or affective benefits from vaping, which is considered a less desirable outcome (i.e., worse outcome).

The 3-item Mean Vaping Injunctive Norms Scale measures participants' perceptions of others' approval or disapproval of their vaping behavior, using a response scale from 1 to 5. Overall scores, which range from 1 to 5, are calculated by averaging the three items. Higher scores indicate stronger perceived disapproval of vaping, which is considered a desirable outcome (i.e., better outcome).

The 3-item Mean Vaping Refusal Self-Efficacy Scale measures a participant's confidence in their ability to refuse vaping in social situations, with response options ranging from 1 to 5. The overall score, also ranging from 1 to 5, is calculated by averaging the three items. Higher scores indicate stronger self-efficacy beliefs in refusing vaping, which is considered a desirable outcome (i.e., better outcome).

Neutral vaping ads: Three neutral (i.e., purely informational and without graphics) vaping video ads developed by the Investigators will be shown to participants at weeks 0, 1, and 2. Ads will be shown in a random order.

This group consists of participants who took part in the pilot phase of the trial prior to its full launch. The purpose of this phase was to pilot test the clinical trial processes and procedures. Participants were recruited separately and not a part of the actual clinical trial.

Total of all reporting groups

The following data do not include participants who identified themselves as a gender identity other than male or female.

The 3-item Susceptibility to Vaping Scale assesses the extent to which adolescents are open to vaping, using a 1 to 4 response option scale. Here, 1 indicates the lowest susceptibility to vaping, and 4 represents the highest, with higher values indicating a greater susceptibility to vaping - essentially, a worse outcome. The overall scale score is determined by averaging the scores of the three items, summing these scores and dividing by 3. This method results in a score range from a minimum of 1 to a maximum of 4.

The FDA's The Real Cost vaping prevention ads - Addiction theme: Three vaping prevention video ads from the FDA's The Real Cost prevention campaign about vaping addiction will be shown to participants at week 0, 1, and 2. Ads will be shown in a random order.

Neutral vaping ads: Three neutral (i.e., purely informational and without graphics) vaping video ads developed by the Investigators will be shown to participants at weeks 0, 1, and 2. Ads will be shown in a random order.

The 1-item mean attention measure assesses the extent to which a participant reports that an advertisement captures their attention. Response options range from 1 to 5, with higher scores indicating stronger attention, which is considered a better outcome.

The 3-item Negative Affect Scale assesses the extent to which an advertisement elicits negative emotions from the participant, such as fear or disgust. Response options range from 1 to 5. The overall scale score is calculated by averaging the scores of the three items, resulting in a minimum possible score of 1 and a maximum of 5. Higher scores indicate stronger negative emotions. In the context of this assessment, higher negative emotions are considered a more effective (better) outcome.

The 3-item Mean Cognitive Elaboration Scale assesses the extent to which participants have thought about the addictiveness or harmfulness of vaping over the past 7 days. Response options range from 1 to 5. The overall scale score is calculated by averaging the three items, with scores ranging from a minimum of 1 to a maximum of 5. Higher scores indicate greater cognitive elaboration, suggesting a more effective engagement with the content (a better outcome).

The 3-item Mean Social Interactions Scale assesses the extent to which a participant has discussed the addictiveness or harmfulness of vaping with others in the past 7 days. Response options range from 1 (0 times) to 6 (11 or more times). The overall scale score is calculated by averaging the three items, resulting in a score range from a minimum of 1 to a maximum of 6. Higher scores indicate more frequent social interactions, which are considered a better outcome.

The 3-item Vaping Health Harm Risk Beliefs Scale assesses the extent to which participants believe that vaping will lead to health harms. Response options range from 1 to 5. The overall scale score is calculated by averaging the three items, with possible scores ranging from a minimum of 1 to a maximum of 5. Higher scores indicate stronger beliefs in the health risks associated with vaping, which is considered a better outcome.

The 3-item Vaping Addiction Risk Beliefs Scale assesses the extent to which participants believe that vaping will lead to addiction. Response options range from 1 to 5. The overall scale score is calculated by averaging the three items, with a score range from 1 to 5. Higher scores indicate stronger beliefs in the risk of addiction due to vaping, which is considered a better outcome.

The 3-item Vaping Attitudes Scale assesses a participant's attitude towards vaping (e.g., good/bad). Response options range from 1 to 5. The overall scale score is calculated by averaging the three items, with scores ranging from 1 to 5. Higher scores indicate a more positive attitude toward vaping, which is considered a less desirable outcome (i.e., worse outcome).

Participants will be asked to report the number of days they vaped over the past 21 days. We chose to retain the continuous measure of the number of days spent vaping rather than dichotomizing this outcome, due to the substantial variability observed in the number of days e-cigarettes were used. A higher value indicates more days that participants vaped, which is considered a less desirable outcome (i.e., worse outcome).

The 1-item Mean Smoking Health Harm Risk Belief Measure assesses the extent to which a participant believes that smoking will lead to health harms. Response options range from 1 to 5, with higher scores indicating stronger beliefs in the health risks associated with smoking, which is considered a desirable outcome (i.e., better outcome).

The 1-item mean smoking health harm risk belief measure assesses the extent to which a participant believes that smoking will lead to health harms. Response options are on a 1 to 5 scale, with higher scores representing a stronger health harm beliefs about smoking, which is a desirable outcome (i.e., better outcome).

The 1-item mean smoking attitude measure assesses a participant's attitude toward smoking (i.e., good/bad). Response options are on a 1 to 5 scale, with higher scores representing a more positive attitude toward smoking, which is considered as less desirable outcome (i.e., worse outcome).

The 3-item Mean Susceptibility to Smoking Cigarettes Scale assesses a participant's susceptibility to smoking cigarettes. Response options range from 1 to 5. The overall scale score is calculated by averaging the three items, with possible scores ranging from 1 to 5. Higher scores indicate a stronger susceptibility to smoking, which is considered a less desirable outcome (i.e., worse outcome).

Participants will be asked to report the number of days they smoked cigarettes over the past 21 days. We chose to retain the continuous measure of the number of days smoking rather than dichotomizing this outcome, due to the substantial variability observed in the number of days cigarettes were used. A higher value indicates more days that participants smoked cigarettes, which is considered a less desirable outcome (i.e., worse outcome).

The 3-item UNC Youth Mean Perceived Message Effectiveness Scale assesses a participant's judgment of an advertisement's impact on their vaping beliefs and behaviors. Response options range from 1 to 5. The overall score is calculated by averaging the three items, with possible scores ranging from 1 to 5. Higher scores indicate that participants perceive the advertisements as more effective (i.e., better outcome).

The 6-item FDA Mean Perceived Message Effectiveness Scale evaluates a participant's overall impressions of an advertisement. Responses are provided on a scale from 1 to 5. The overall scale score is calculated by averaging these six items, resulting in a possible range of 1 to 5. Higher scores indicate that participants found the advertisements to be more informative (i.e., better outcome).

The 3-item Avoidance Scale measures the degree to which a participant wishes to avoid engaging with an advertisement. Responses are provided on a scale from 1 to 5. The overall score is calculated by summing the scores of the three items and then dividing by 3, resulting in a possible range of 1 to 5. Higher scores indicate greater avoidance, which is considered a less desirable outcome (i.e., worse outcome).

The 1-item reactance measure evaluates the degree to which an ad annoys participants, using a response scale from 1 to 5. Higher scores indicate greater reactance to the ad, representing a less favorable outcome.

The 3-item Mean Vaping Social Enhancement Beliefs Scale measures participants' perceptions of the social benefits of vaping, such as fitting in better with friends. Responses are on a 1 to 5 scale, with overall scores calculated by averaging the three items. Scores range from 1 to 5, where higher scores indicate a stronger belief in the social benefits of vaping, a less desirable outcome (i.e., worse outcome).

The 3-item Mean Vaping Affect Regulation Beliefs Scale evaluates participants' beliefs about the experiential benefits of vaping, such as feeling good. Responses are recorded on a 1 to 5 scale. The overall score, which also ranges from 1 to 5, is calculated by averaging the three items. Higher scores indicate that participants expect more significant emotional or affective benefits from vaping, which is considered a less desirable outcome (i.e., worse outcome).

The 3-item Mean Vaping Injunctive Norms Scale measures participants' perceptions of others' approval or disapproval of their vaping behavior, using a response scale from 1 to 5. Overall scores, which range from 1 to 5, are calculated by averaging the three items. Higher scores indicate stronger perceived disapproval of vaping, which is considered a desirable outcome (i.e., better outcome).

The 3-item Mean Vaping Refusal Self-Efficacy Scale measures a participant's confidence in their ability to refuse vaping in social situations, with response options ranging from 1 to 5. The overall score, also ranging from 1 to 5, is calculated by averaging the three items. Higher scores indicate stronger self-efficacy beliefs in refusing vaping, which is considered a desirable outcome (i.e., better outcome).

The FDA's The Real Cost vaping prevention ads - Addiction theme: Three vaping prevention video ads from the FDA's The Real Cost prevention campaign about vaping addiction will be shown to participants at week 0, 1, and 2. Ads will be shown in a random order.

Neutral vaping ads: Three neutral (i.e., purely informational and without graphics) vaping video ads developed by the Investigators will be shown to participants at weeks 0, 1, and 2. Ads will be shown in a random order.

This group consists of participants who took part in the pilot phase of the trial prior to its full launch. The purpose of this phase was to pilot test the clinical trial processes and procedures. Participants were recruited separately and not a part of the actual clinical trial.