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  2. Astigmatism - Wikipedia

    en.wikipedia.org/wiki/Astigmatism

    Astigmatism may be corrected with eyeglasses, contact lenses, or refractive surgery. Glasses are the simplest and safest, although contact lenses can provide a wider field of vision . Refractive surgery can eliminate the need to wear corrective lenses altogether by permanently changing the shape of the eye but, like all elective surgery, comes ...

  3. Bessel's correction - Wikipedia

    en.wikipedia.org/wiki/Bessel's_correction

    Bessel's correction. In statistics, Bessel's correction is the use of n − 1 instead of n in the formula for the sample variance and sample standard deviation, [1] where n is the number of observations in a sample. This method corrects the bias in the estimation of the population variance. It also partially corrects the bias in the estimation ...

  4. Coupon collector's problem - Wikipedia

    en.wikipedia.org/wiki/Coupon_collector's_problem

    In probability theory, the coupon collector's problem refers to mathematical analysis of "collect all coupons and win" contests. It asks the following question: if each box of a given product (e.g., breakfast cereals) contains a coupon, and there are n different types of coupons, what is the probability that more than t boxes need to be bought ...

  5. Coupon - Wikipedia

    en.wikipedia.org/wiki/Coupon

    Coupon. In marketing, a coupon is a ticket or document that can be redeemed for a financial discount or rebate when purchasing a product . Customarily, coupons are issued by manufacturers of consumer packaged goods [1] or by retailers, to be used in retail stores as a part of sales promotions. They are often widely distributed through mail ...

  6. Volume correction factor - Wikipedia

    en.wikipedia.org/wiki/Volume_Correction_Factor

    In thermodynamics, the Volume Correction Factor (VCF), also known as Correction for the effect of Temperature on Liquid (CTL), is a standardized computed factor used to correct for the thermal expansion of fluids, primarily, liquid hydrocarbons at various temperatures and densities. [1] [2] It is typically a number between 0 and 2, rounded to ...

  7. Ophthalmic trial frame - Wikipedia

    en.wikipedia.org/wiki/Ophthalmic_trial_frame

    ophthalmic trial frame is used to hold lenses and other accessories during correction of refractive errors. Test of. Visual acuity. A trial frame is a tool used by ophthalmic professionals like ophthalmologists and optometrists. It is basically an adjustable spectacle frame with multiple cells, used to hold corrective lenses, and other ...

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