Eye chart number). The denominator indicates the distance in feet at which a person with normal vision could stand to correctly identify the same symbols identified by the person tested. For example, a visual acuity of 20/20 is considered normal. Numerous types of eye charts exist and are used in various situations. For example, the Snellen chart is designed for use at 6 meters or 20 feet, and is thus appropriate for testing distance vision. There is often also a need to test a subject's vision at near or occupational tasks (such as reading or computer use). For these situations, a Rosenbaum
X̅ and s chart on the other hand, the sample variability is "not" in statistical control, then the entire process is judged to be not in statistical control regardless of what the formula_7 chart indicates. When samples collected from the process are of unequal sizes (arising from a mistake in collecting them, for example), there are two approaches: X̅ and s chart In statistical quality control, the formula_7 and s chart is a type of control chart used to monitor variables data when samples are collected at regular intervals from a business or industrial process. The chart is advantageous in the following situations: The