Snellen chart H, K, O, S, 3, U, Y, A, C, E, G, L, 2. The normal Snellen chart is printed with eleven lines of block letters. The first line consists of one very large letter, which may be one of several letters, for example E, H, or N. Subsequent rows have increasing numbers of letters that decrease in size. A person taking the test covers one eye from 6 metres or 20 feet away, and reads aloud the letters of each row, beginning at the top. The smallest row that can be read accurately indicates the visual acuity in that specific
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