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Vertex distance is the distance between the back surface of a corrective lens, i.e. glasses (spectacles) or contact lenses, and the front of the cornea. Increasing or decreasing the vertex distance changes the optical properties of the system, by moving the focal point forward or backward, effectively changing the power of the lens relative to ...
Snellen chart is used to estimate visual acuity (last three rows are 20/15, 20/13 and 20/10) A Snellen chart is an eye chart that can be used to measure visual acuity. Snellen charts are named after the Dutch ophthalmologist Herman Snellen who developed the chart in 1862 as a measurement tool for the acuity formula developed by his professor ...
A pie chart (or a circle chart) is a circular statistical graphic which is divided into slices to illustrate numerical proportion. In a pie chart, the arc length of each slice (and consequently its central angle and area) is proportional to the quantity it represents. While it is named for its resemblance to a pie which has been sliced, there ...
The standard deviation σ of X is defined as which can be shown to equal. Using words, the standard deviation is the square root of the variance of X . The standard deviation of a probability distribution is the same as that of a random variable having that distribution. Not all random variables have a standard deviation.
History. The chart was designed by Ian Bailey and Jan E. Lovie-Kitchin at the National Vision Research Institute of Australia. They described their motivation for designing the LogMAR chart as follows: "We have designed a series of near vision charts in which the typeface, size progression, size range, number of words per row and spacings were chosen in an endeavour to achieve a ...
A growth chart is used by pediatricians and other health care providers to follow a child's growth over time. Growth charts have been constructed by observing the growth of large numbers of healthy children over time. The height, weight, and head circumference of a child can be compared to the expected parameters of children of the same age and ...
Ballistic chart data are typically given in angular measurements with units in either milliradians (mil/mrad) or minutes of arc (MOA), arranged in a table format with the rows representing different reference distances and the columns corresponding to categories of information (e.g. angular deviations, actual drop/drift distance, "click" count ...
Shewhart individuals control chart. In statistical quality control, the individual/moving-range chart is a type of control chart used to monitor variables data from a business or industrial process for which it is impractical to use rational subgroups. [1] The chart is necessary in the following situations: [2] : 231.