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Abstract
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Before
This study investigates whether personalised, progressively increasing step thresholds can enhance engagement in an incentive-based physical activity (PA) programme administered by a private health insurer. The intervention is designed to improve PA adherence among individuals who have linked an activity tracker but exhibited low or inconsistent engagement with standard step-based goals.
A randomised controlled trial (RCT) will be conducted with 20,200 adult members of the insurer’s wellness programme. Participants will be randomly assigned to one of five conditions: (1) Standard Control (fixed step goals), (2) Variable Step Threshold – Fast Progression, (3) Variable Step Threshold – Slow Progression, (4) Variable Step & Point Threshold – Fast Progression, and (5) Variable Step & Point Threshold – Slow Progression. Treatment groups will receive adaptive step targets that increase gradually based on prior engagement, combined with weekly financial incentives (£5 vouchers) for goal completion.
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After
This study evaluates whether personalised step-to-points thresholds improve engagement in an insurer-linked physical activity incentive programme in the United Kingdom. The trial was embedded in a digital app platform operating alongside the insurer’s standard rewards programme.
Eligible adult members with low prior recorded physical activity were invited to join the study app. Participants entered a six-week baseline period followed by a six-week intervention period, with rolling enrolment between November 2023 and February 2024. After post-baseline eligibility confirmation, 714 participants were randomised within insurer-defined engagement strata (Unengaged vs Low engaged).
Randomisation was stratified by engagement group and implemented automatically within the study app. In the Low engaged stratum, participants were allocated to control (CL) or personalised thresholds with bonus (TL). In the Unengaged stratum, participants were allocated to control (CU), personalised thresholds with streak bonus (TU), or personalised thresholds without streak bonus (TU no bonus). Control groups remained on the insurer’s standard step-to-points schedule. Personalised groups started on more attainable step thresholds and could progress toward less generous schedules according to pre-specified platform rules. Participants received a £5 weekly Amazon voucher for meeting the weekly goal (>=12 points), and bonus-eligible arms also received a £15 streak bonus for meeting the goal in all six intervention weeks.
The primary outcome was participant-level mean weekly goal achievement during intervention weeks 0 to 5 (observed weeks only). Secondary outcomes included participant-level mean weekly steps and an indicator for achieving the weekly goal at least once. The primary analysis pooled bonus-treatment arms (TU and TL) versus pooled controls (CU and CL), with a secondary comparison within the Unengaged stratum.
In the main pooled comparison, personalised thresholds with a bonus improved weekly goal attainment but did not produce a statistically detectable increase in mean weekly steps over the six-week intervention period. Follow-up observation in platform data was incomplete and differed by arm, so missing-data sensitivity analyses were conducted and reported.
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Trial Start Date
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Before
March 01, 2023
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November 20, 2023
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Trial End Date
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Before
April 01, 2024
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After
March 03, 2024
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Last Published
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Before
March 26, 2025 08:21 AM
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After
February 23, 2026 05:34 AM
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Intervention (Public)
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Before
Intervention Description
This study examines whether personalised step goal progression can enhance engagement in an incentive-based physical activity (PA) programme run by a private health insurer. The intervention targets adults with low or inconsistent PA engagement, defined as individuals who have linked an activity tracker but have not consistently met weekly PA goals in the preceding three months.
Participants were randomly assigned to one of five groups:
Control Group (Standard Goals)
Participants received the standard fixed step goals and incentive structure provided by the insurer’s wellness programme.
Treatment 1-1: Variable Step Threshold – Fast Progression
Participants started with a low daily step goal (2,000 steps) that increased every two weeks:
Weeks 1-2: 2,000 steps per day (3 points)
Weeks 3-4: 3,000 steps per day (3 points)
Weeks 5-6: 5,000 steps per day (3 points)
Weeks 7-8: 7,000 steps per day (3 points)
Treatment 1-2: Variable Step Threshold – Slow Progression
Similar to Treatment 1-1, but step targets increased at a slower rate:
Weeks 1-3: 3,000 steps per day (3 points)
Weeks 4-6: 5,000 steps per day (3 points)
Weeks 7-8: 7,000 steps per day (3 points)
Treatment 2-1: Variable Step & Point Threshold – Fast Progression
Participants followed the same fast step progression as Treatment 1-1, but earned higher rewards at early stages:
Weeks 1-2: 3,000 steps per day (5 points)
Weeks 3-4: 5,000 steps per day (5 points)
Weeks 5-6: 5,000 steps per day (3 points)
Weeks 7-8: 7,000 steps per day (3 points)
Treatment 2-2: Variable Step & Point Threshold – Slow Progression
Participants followed the same slow step progression as Treatment 1-2, but with an adjusted points structure:
Weeks 1-3: 5,000 steps per day (5 points)
Weeks 4-6: 5,000 steps per day (3 points)
Weeks 7-8: 7,000 steps per day (3 points)
Incentive Structure:
Participants in all groups were eligible for a weekly £5 Amazon voucher upon achieving their PA goals.
If participants failed to meet their assigned step goal, they remained at the same threshold or moved backward in step targets.
This intervention seeks to evaluate whether adaptive step thresholds—with varying progression speeds and incentive structures—improve PA engagement, adherence, and habit formation compared to a fixed goal approach.
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After
This study evaluated personalised step-to-points thresholds in a UK health insurer-linked trial app operating alongside the insurer’s standard rewards programme. Participants were adults with very low or low prior recorded physical activity (insurer-defined “Unengaged” and “Low engaged” groups) who downloaded the study app and consented to data use. After a six-week baseline period in the trial platform (weeks -6 to -1) used for eligibility confirmation, participants were randomised within engagement strata.
The trial platform awarded points for device-recorded activity (steps and workouts), with a weekly goal of at least 12 points. Participants received a £5 Amazon voucher for each intervention week in which they achieved the weekly goal. In bonus-eligible arms, participants also received a £15 Amazon voucher if they achieved the weekly goal in all six intervention weeks (weeks 0 to 5).
The intervention manipulated the step-to-points schedule (levels 0 to 5). Level 5 was the standard schedule used in the insurer’s usual programme. Personalised arms started on a more generous schedule and could move toward less generous schedules over time according to pre-specified platform rules. Progression required (i) achieving the weekly goal in the preceding week and (ii) meeting a rolling six-week average points threshold for the next level. Participants who failed to achieve the weekly goal for two consecutive weeks moved back one level (to a more generous schedule).
Trial arms (stratified by engagement group) were:
Low engaged stratum:
- CL (control, low engaged): standard schedule (level 5 throughout)
- TL (treatment, low engaged): personalised thresholds with streak bonus; started on level 3 and could transition across levels under the platform rule; eligible for the £15 streak bonus
Unengaged stratum:
- CU (control, unengaged): standard schedule (level 5 throughout)
- TU (treatment, unengaged): personalised thresholds with streak bonus; started on level 1 and could transition across levels under the platform rule; eligible for the £15 streak bonus
- TU no bonus (treatment, unengaged): same personalised threshold progression as TU, but not eligible for the £15 streak bonus
No group started on level 0. The intervention period lasted six weeks (weeks 0 to 5), following the six-week baseline period.
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Intervention Start Date
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Before
April 01, 2023
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January 01, 2024
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Intervention End Date
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Before
June 01, 2023
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After
March 03, 2024
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Primary Outcomes (End Points)
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Before
Daily Step Count (Continuous Variable)
Total number of steps recorded per participant per day.
Measured using activity tracking devices throughout the 8-week intervention period.
Weekly Physical Activity Goal Achievement (Binary Variable)
Whether a participant meets their assigned step goal for at least 4 out of 7 days in a given week.
Assessed weekly over the intervention period.
Step Goal Adherence Over Time (Continuous & Binary Variable)
Continuous: Number of days per week participants meet their assigned step goal.
Binary: Whether step goals are met for at least 4 out of 7 days in the final two weeks of the study.
Programme Dropout Rate (Binary Variable)
Whether a participant stops engaging before the end of the 8-week period.
Defined as no recorded steps for ≥7 consecutive days.
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After
Mean weekly goal achievement during intervention weeks 0 to 5 (primary endpoint).
Participant-level mean of a weekly indicator equal to 1 if the participant accumulated at least 12 trial-platform points in that study week, and 0 otherwise, averaged over observed intervention weeks only (weeks 0 to 5). Weeks with missing weekly goal achievement are treated as unobserved in the main specification. This is the primary endpoint for the main pooled ITT comparison (TU + TL vs CU + CL).
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Primary Outcomes (Explanation)
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Before
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After
Weekly goal achievement is recorded by the trial platform from the participant’s weekly points total. Because step-to-points schedules differ across arms by design, this endpoint captures success in meeting the assigned weekly goal under the participant’s allocated schedule (behavioural engagement/goal attainment), not attainment of a common absolute step threshold across arms. The participant-level primary endpoint is the mean of the weekly goal-achievement indicator over intervention weeks 0 to 5 using observed weeks only.
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Experimental Design (Public)
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Before
This study is a randomised controlled trial (RCT) evaluating the impact of progressively increasing step thresholds on physical activity (PA) engagement. The intervention is delivered through a private health insurer’s wellness platform and targets adults with low or inconsistent PA engagement, defined as individuals who have linked an activity tracker but have not consistently met weekly PA goals in the preceding three months.
Study Design & Methodology
This is a prospective, parallel-arm RCT in which participants are randomly assigned to one of five experimental arms. The trial assesses whether gradually increasing step goals, with and without adjusted point thresholds, improve engagement, adherence, and habit formation compared to a fixed-goal approach.
1. Randomisation & Stratification
Participants were randomly assigned using block randomisation stratified by:
Baseline PA level (low, medium, high)
Demographics (age, gender)
This ensures balanced treatment allocation across key participant characteristics.
2. Intervention Arms
Participants are assigned to one of five groups:
Control Group (Standard Goals)
Receives fixed daily step goals as per standard programme conditions.
Treatment 1-1: Variable Step Threshold – Fast Progression
Step goal increases every two weeks: 2,000 → 3,000 → 5,000 → 7,000 steps/day.
Treatment 1-2: Variable Step Threshold – Slow Progression
Step goal increases at a slower rate: 3,000 → 5,000 → 7,000 steps/day over 8 weeks.
Treatment 2-1: Variable Step & Point Threshold – Fast Progression
Same fast step progression, but higher points in early stages:
Weeks 1-2: 3,000 steps/day, 5 points
Weeks 3-4: 5,000 steps/day, 5 points
Weeks 5-6: 5,000 steps/day, 3 points
Weeks 7-8: 7,000 steps/day, 3 points
Treatment 2-2: Variable Step & Point Threshold – Slow Progression
Same slow step progression, but with an adjusted points structure:
Weeks 1-3: 5,000 steps/day, 5 points
Weeks 4-6: 5,000 steps/day, 3 points
Weeks 7-8: 7,000 steps/day, 3 points
3. Incentive Structure
Participants in all groups are eligible for a weekly £5 Amazon voucher upon meeting step goals.
If participants fail to meet their assigned goal, their step target remains the same or moves backward.
Causal Identification Strategy
To ensure robust causal inference, the study employs multiple estimation techniques:
Intention-to-Treat (ITT) Analysis
Estimates the impact of assignment to treatment groups, regardless of adherence.
Treatment-on-the-Treated (TOT) Analysis
Adjusts for non-compliance and dropout using inverse probability weighting (IPW).
Difference-in-Differences (DiD)
Compares pre- and post-intervention step counts between treatment and control groups.
Heterogeneous Treatment Effects
Explores differences by baseline PA level, demographics, and dropout risk.
Data Collection & Measurement
Data Source: Automatically collected via wearable fitness devices linked to the wellness platform.
Primary Outcomes:
Daily step count (measured continuously).
Weekly goal achievement (binary outcome).
Step goal adherence over time (measured in early vs. late intervention periods).
Programme dropout rate (binary outcome).
Secondary Outcomes:
Post-intervention PA levels (assessing sustained behaviour change).
Engagement with incentives (tracking participation in rewards scheme).
Habit formation indicators (measuring consistency and persistence of PA behaviour).
Long-Term Analysis & Post-Intervention Effects
To evaluate the sustained impact of progressive step thresholds, the study includes a long-term follow-up phase analyzing post-intervention behavior.
1. Post-Incentive Physical Activity (Long-Term Outcomes)
Continuous: Average daily step count in the four weeks following the intervention.
Binary: Whether a participant maintains ≥5,000 steps per day for at least 4 days per week post-intervention.
2. Habit Formation & Retention Analysis
Persistence of Routine: Evaluates whether participants maintain similar PA levels without financial incentives.
PA Consistency: Assesses reduction in daily step count variability (i.e., fewer extreme fluctuations).
Automaticity of PA Behavior: Measures whether step targets are met without ongoing intervention prompts.
3. Causal Identification for Long-Term Effects
Event Study Approach:
Estimates dynamic treatment effects at multiple time points post-intervention.
Compares step counts before, during, and after the experiment to determine whether effects persist or fade.
Tests for placebo effects using pre-treatment activity data.
Panel Regression with Individual Fixed Effects:
Controls for time-invariant individual characteristics (e.g., baseline fitness levels).
Models post-intervention changes in PA relative to pre-treatment trends.
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After
This study is a randomised controlled trial embedded in a UK health insurer-linked digital rewards environment. Participants were members with low prior recorded physical activity, identified using insurer engagement classifications (“Unengaged” and “Low engaged”), invited by email, and enrolled in a study app. Participants were enrolled on a rolling basis between November 2023 and February 2024. Study time was indexed to each participant’s intervention start date. The design included a six-week baseline period (weeks -6 to -1) and a six-week intervention period (weeks 0 to 5).
After consent and app download, six weeks of trial-platform baseline data were used to confirm eligibility and exclude participants whose observed baseline activity was inconsistent with the intended low-activity sample. Randomisation was then implemented automatically within the study app after baseline eligibility confirmation. Randomisation was stratified by insurer engagement stratum (Unengaged vs Low engaged). Intended allocation was 1:1 in the Low engaged stratum (CL vs TL) and 1:1:1 in the Unengaged stratum (CU vs TU vs TU no bonus). Allocation was computer-generated and concealed prior to assignment. Outcomes were recorded automatically by the trial platform. Participants could view their own targets and rewards in the app but were not informed of arm labels or other participants’ schedules.
The intervention varied the step-to-points schedule used to earn weekly points. Control groups (CL and CU) remained on the standard schedule (level 5). Personalised groups began on more generous schedules and could progress toward less generous schedules under pre-specified level transition rules. All groups were eligible for a £5 Amazon voucher for achieving the weekly goal (>=12 points) in a given week. TU and TL were additionally eligible for a £15 bonus for achieving the weekly goal in all six intervention weeks; TU no bonus was not bonus-eligible.
The primary endpoint is the participant-level mean weekly goal-achievement indicator over intervention weeks 0 to 5 (observed weeks only). Secondary endpoints are participant-level mean weekly steps over intervention weeks 0 to 5 (observed weeks only) and an indicator for achieving the weekly goal at least once during weeks 0 to 5. The main ITT comparison pools bonus-treatment arms (TU and TL) versus pooled controls (CU and CL). A secondary comparison is conducted within the Unengaged stratum (TU vs TU no bonus vs CU). Analyses are estimated at the participant level using assignment-based (ITT) models; missing platform observation is characterised separately and addressed in sensitivity analyses.
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Randomization Method
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Before
Randomization was conducted using a computer-generated process.
Participants were randomly assigned to treatment arms at the time of enrollment.
The original study plan proposed block randomization stratified by baseline step counts and demographic characteristics, but final implementation details should be verified
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After
Randomisation was implemented automatically within the study app using a computer-generated allocation procedure after six-week baseline eligibility confirmation. Randomisation was stratified by insurer engagement stratum (Unengaged vs Low engaged), with intended allocation 1:1 in the Low engaged stratum and 1:1:1 in the Unengaged stratum. Allocation was concealed prior to assignment. Outcomes were recorded automatically by the trial platform.
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Randomization Unit
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individual
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After
Individual participant (randomisation occurred at the participant level within engagement strata).
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Planned Number of Clusters
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20,200
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After
Not applicable (individual randomisation; no clusters)
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Planned Number of Observations
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Before
Planned number of observations: Up to 1,131,200 individual-day observations (20,200 participants tracked daily for 8 weeks).
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Individual-level randomised sample: 714 participants (final realised sample). The study design includes up to 12 participant-weeks per participant (6 baseline + 6 intervention), implying up to 8,568 participant-week windows before outcome-specific non-observation. Analyses are primarily conducted at the participant level using participant-level summary outcomes over intervention weeks 0 to 5
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Sample size (or number of clusters) by treatment arms
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Before
Total sample size: 20,200 participants.
Participants were randomly assigned to one of five treatment arms. Exact allocation per arm will be updated once internal records are verified.
Based on the study design, we anticipate approximately equal allocation (~4,040 per arm), but final numbers may vary due to data constraints.
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After
Final randomised sample (individuals): 714 participants.
Randomised arm sizes (realised):
CL (control, Low engaged): 205
TL (personalised targets + streak bonus, Low engaged): 189
CU (control, Unengaged): 117
TU (personalised targets + streak bonus, Unengaged): 118
TU no bonus (personalised targets, no streak bonus, Unengaged): 85
Participants were randomised within engagement strata. Intended allocation was 1:1 in Low engaged (CL vs TL) and 1:1:1 in Unengaged (CU vs TU vs TU no bonus). Realised allocation differed slightly from intended ratios due to observed enrolment and eligibility within strata. App entrants before post-baseline eligibility confirmation: 997; excluded after baseline eligibility confirmation: 283.
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Secondary Outcomes (End Points)
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Before
1. Post-Intervention Physical Activity Levels (Continuous & Binary Variables)
Continuous: Average daily step count during the four weeks following the intervention.
Binary: Whether a participant maintains ≥5,000 steps per day for at least 4 days per week post-intervention.
2. Step Goal Progression Patterns (Continuous Variable)
Number of times a participant progresses, stagnates, or regresses in step goal levels throughout the intervention.
3. Response to Step Goal Increases (Continuous Variable)
Change in daily step counts following an increase in assigned step thresholds.
4. Engagement with Incentive Structure (Continuous & Binary Variables)
Continuous: Number of weeks participants earn the £5 voucher for goal achievement.
Binary: Whether a participant claims the incentive at least four times during the intervention.
5. Habit Formation Metrics (Binary & Continuous Variables)
Automaticity of Physical Activity Behavior
Proportion of participants who continue meeting step goals without financial incentives (measured in post-intervention weeks).
PA Consistency
Reduction in daily step count variability (i.e., fewer extreme fluctuations in step levels).
Persistence of Routine
Whether participants continue walking at similar times and intensities post-intervention.
6. Heterogeneous Treatment Effects (Interaction Variables)
Differential treatment effects by:
Baseline PA levels (low, medium, high).
Demographics (age, gender).
Device type (smartphone vs. wearable).
Dropout risk (propensity score-matched subgroups).
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After
Mean weekly steps during intervention weeks 0 to 5 (observed weeks only).
Participant-level mean weekly steps over intervention weeks 0 to 5, calculated using observed weekly steps only. This outcome is defined for participants with at least one observed weekly steps value during weeks 0 to 5.
Any weekly goal achieved at least once during intervention weeks 0 to 5.
Indicator equal to 1 if the participant achieved the weekly goal (>=12 points) in at least one intervention week (weeks 0 to 5), and 0 otherwise, among participants with at least one observed intervention week for goal achievement.
Platform observation / non-observation patterns (descriptive and sensitivity-related).
Week-by-week platform observation rates for goal achievement and steps, endline observation (week 5), and mean number of observed intervention weeks, by arm. These are used to characterise missingness/non-observation in trial-platform outcomes.
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Secondary Outcomes (Explanation)
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After
Missingness in this study reflects non-observation in the trial-platform data (for example, non-use of the app, missing wearable linkage/synchronisation, or failed data transmission), rather than formal withdrawal. Main ITT outcomes are defined using observed intervention weeks only, and sensitivity analyses examine alternative assumptions for missing weekly outcomes.
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Pi as first author
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No
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Yes
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