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  2. Snellen chart - Wikipedia

    en.wikipedia.org/wiki/Snellen_chart

    In the most familiar acuity test, a Snellen chart is placed at a standard distance: 6 metres. At this distance, the symbols on the line representing "normal" acuity subtend an angle of five minutes of arc, and the thickness of the lines and of the spaces between the lines subtends one minute of arc. This line, designated 6/6 (or 20/20), is the ...

  3. Percentile - Wikipedia

    en.wikipedia.org/wiki/Percentile

    Each standard deviation represents a fixed percentile. Thus, rounding to two decimal places, −3σ is the 0.13th percentile, −2σ the 2.28th percentile, −1σ the 15.87th percentile, 0σ the 50th percentile (both the mean and median of the distribution), +1σ the 84.13th percentile, +2σ the 97.72nd percentile, and +3σ the 99

  4. Visual acuity - Wikipedia

    en.wikipedia.org/wiki/Visual_acuity

    Eye examination for visual acuity. Visual acuity is a measure of the spatial resolution of the visual processing system. VA, as it is sometimes referred to by optical professionals, is tested by requiring the person whose vision is being tested to identify so-called optotypes – stylized letters, Landolt rings, pediatric symbols, symbols for the illiterate, standardized Cyrillic letters in ...

  5. Golden ratio - Wikipedia

    en.wikipedia.org/wiki/Golden_ratio

    The decimal expansion of the golden ratio [1] has been calculated to an accuracy of ten trillion (=) digits. [ 66 ] In the complex plane , the fifth roots of unity z = e 2 π k i / 5 {\displaystyle z=e^{2\pi ki/5}} (for an integer k {\textstyle k} ) satisfying z 5 = 1 {\displaystyle z^{5}=1} are the vertices of a pentagon.

  6. Order of magnitude - Wikipedia

    en.wikipedia.org/wiki/Order_of_magnitude

    An order-of-magnitude estimate of a variable, whose precise value is unknown, is an estimate rounded to the nearest power of ten. For example, an order-of-magnitude estimate for a variable between about 3 billion and 30 billion (such as the human population of the Earth) is 10 billion. To round a number to its nearest order of magnitude, one ...

  7. Brix - Wikipedia

    en.wikipedia.org/wiki/Brix

    Measuring brix and percent acidity of a sudachi. Degrees Brix(symbol °Bx) is a measure of the dissolved solids in a liquid, and is commonly used to measure dissolved sugarcontent of an aqueous solution.[1] One degree Brix is 1 gram of sucrosein 100 grams of solution and represents the strength of the solution as percentage by mass.

  8. List of drill and tap sizes - Wikipedia

    en.wikipedia.org/wiki/List_of_drill_and_tap_sizes

    Below is a comprehensive drill and tap size chart for all drills and taps, imperial and metric, up to 36.5 millimetres (1.44 in) in diameter. In manufactured parts, holes with female screw threads are often needed; they accept male screws to facilitate the building and fastening of a finished assembly.

  9. 16:9 aspect ratio - Wikipedia

    en.wikipedia.org/wiki/16:9_aspect_ratio

    16:9 is a widescreen aspect ratio with a width of 16 units and height of 9 units. Once seen as an "exotic" aspect ratio, [ 1 ] since 2009, it has become the most common aspect ratio for televisions and computer monitors , and is also the universal standard image format for the universal 1080p , 2160p and 4320p formats.