Revise Human factors and ergonomics for IB Design Technology (1.1)

Although often used interchangeably, 'ergonomics' and 'human factors' have distinct focuses. Ergonomics is primarily concerned with the physical fit between the user and the product. Think of the shape of a mouse that prevents wrist strain or the height of an office chair. Human Factors is a broader field that encompasses ergonomics but also includes psychological (cognitive) factors. This involves how users perceive information, make decisions, and react to feedback from a product, such as the layout of a car's dashboard or the intuitiveness of a software interface.

To design for a physical fit, we need data. Anthropometry provides this data by measuring human body dimensions. This data is collected for specific populations and is presented statistically, often using percentiles. A percentile is a measure indicating the value below which a given percentage of observations in a group of observations falls. For example, the 75th percentile for male height means that 75% of the male population is at or below that height.

To find a specific percentile value ($P_x$) when you have the mean ($\mu$) and standard deviation ($\sigma$) of a normally distributed dataset, you can use the Z-score from a standard table: $P_x = \mu + (Z \times \sigma)$

Beyond static measurements, effective design considers how the human body and mind function over time. Physiological factors relate to bodily functions and tolerances. This includes muscle strength, endurance, the effects of temperature, noise, and vibration on performance and comfort. For example, a power tool's design must consider vibration levels to prevent long-term nerve damage (Hand-Arm Vibration Syndrome). Psychological factors concern the user's mental processes. This involves how information is presented (clarity of symbols, text size), the mental effort required (cognitive load), and how the design influences emotion and behaviour. A well-designed app icon, for instance, is quickly recognisable and communicates its function effectively.