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The ARIA WiFi Smart Scale is a body analyzer that measures body weight and uses bioelectrical impedance analysis (BIA) technology to estimate body fat percentage in generally healthy individuals 10 years of age or older. It is intended for home use only.

ARIA is a body weight scale and a body fat analyzer that operates by using a low, safe, battery-generated electrical current through the body (using a bioelectrical impedance analysis technique) to provide body fat and body weight information. After the user registers their scale, the scale automatically recognizes the subject based on body weight and body fat readings. ARIA contains a WiFi module (802.11 module) that allows it to connect to the Internet in the user's home. The module provides a complementary interface to the Fitbit website. Body weight and body fat measurements are independent of internet communication after initial product registration.

The ARIA scale automatically measures body weight and body fat composition. The scale recognizes the user based on previous weight readings, and can accept up to eight (8) different users. The 16 most recent readings are kept in memory on the scale and readings are also transmitted to the user's optional fitbit.com personal account for trending. If users have similar weight, the proper identity can be selected by tapping the scale.

Here's a breakdown of the acceptance criteria and study information for the Fitbit ARIA WiFi Smart Scale, based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria for the ARIA WiFi Smart Scale are established not through explicit numerical thresholds but by demonstrating substantial equivalence to a predicate device (Withings Smart Body Scale K121971) and showing that its body fat measurements are not statistically different from the predicate, with variation within an acceptable range.

2. Sample Size Used for the Test Set and Data Provenance

• Sample Size for Test Set: 50 subjects (25 male and 25 female).
• Data Provenance: The study was a "small comparative clinical study" comparing the ARIA WiFi Smart Scale to the predicate device. The text does not specify the country of origin but implies it was conducted by the manufacturer or a contracted clinical research organization. The study design strongly suggests it was prospective as it involved collecting new data for direct comparison between the two devices.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts

The study does not establish an independent "ground truth" against which the device performance is measured in the classical sense (e.g., DEXA or underwater weighing). Instead, the performance of the ARIA device is compared directly against the predicate device (Withings Smart Body Scale K121971) as the reference. Therefore, there were no experts used to establish a separate ground truth for the test set. The predicate device's measurements serve as the comparator.

4. Adjudication Method for the Test Set

Not applicable. This was a direct comparison study between a new device and a predicate device. There was no complex labeling or interpretation by multiple human readers requiring adjudication. The study involved objective measurements of body fat percentage from both devices.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done, If So, What Was the Effect Size of How Much Human Readers Improve with AI vs. Without AI Assistance

No, an MRMC comparative effectiveness study was not done. This device (Fitbit ARIA WiFi Smart Scale) is a standalone measurement device for body weight and body fat, not an AI-assisted diagnostic tool that aids human readers. The study performed was a direct comparison of its measurement accuracy against a predicate device.

6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done

Yes, a standalone performance study was done. The clinical performance testing compared the ARIA WiFi Smart Scale's measurements of body fat composition directly against the measurements from the predicate device. This is a standalone comparison as it assesses the device's output independently. The device's primary function is to measure and display these values, which are then transmitted to a user's account for tracking, but the core performance evaluation focuses on the accuracy of these direct measurements.

7. The Type of Ground Truth Used

The "ground truth" for the clinical performance study was the measurements obtained from the predicate device (Withings Smart Body Scale K121971). The study aimed to demonstrate that the ARIA device's measurements were not statistically different from those of the legally marketed predicate device. While BIA is an estimation method itself, for the purpose of demonstrating substantial equivalence, the predicate device's output serves as the comparative reference.

8. The Sample Size for the Training Set

The document does not mention a training set or any machine learning/AI model that would require a distinct training set. The ARIA WiFi Smart Scale uses Bioelectrical Impedance Analysis (BIA) technology, which is a well-established method, not typically relying on a separately described "training set" in the context of regulatory submissions for this type of device. The description focuses on its sensor technology and comparison to a predicate.

9. How the Ground Truth for the Training Set Was Established

As no training set is mentioned or implied for a machine learning model, this question is not applicable. The device relies on physical principles of bioelectrical impedance.

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