To calculate the overall star rating and percentage breakdown by star, we don’t use a simple average. Instead, our system considers things like how recent a review is and if the reviewer bought the item on Amazon. It also analyses reviews to verify trustworthiness.
I am a consultant and used to carry this around with me everywhere. However, after using this for about two years, the scale stopped being accurate. AT first I thought it had to do with the batteries but I found out that this wasn't the case after replacing them. Expect to replace this scale every couple of years.