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  2. Darcy friction factor formulae - Wikipedia

    en.wikipedia.org/wiki/Darcy_friction_factor_formulae

    Churchill equation [24] (1977) is the only equation that can be evaluated for very slow flow (Reynolds number < 1), but the Cheng (2008), [25] and Bellos et al. (2018) [8] equations also return an approximately correct value for friction factor in the laminar flow region (Reynolds number < 2300). All of the others are for transitional and ...

  3. Propagation of uncertainty - Wikipedia

    en.wikipedia.org/wiki/Propagation_of_uncertainty

    Any non-linear differentiable function, (,), of two variables, and , can be expanded as + +. If we take the variance on both sides and use the formula [11] for the variance of a linear combination of variables ⁡ (+) = ⁡ + ⁡ + ⁡ (,), then we obtain | | + | | +, where is the standard deviation of the function , is the standard deviation of , is the standard deviation of and = is the ...

  4. Significant figures - Wikipedia

    en.wikipedia.org/wiki/Significant_figures

    If the n + 1 digit is greater than 5 or is 5 followed by other non-zero digits, add 1 to the n digit. For example, if we want to round 1.2459 to 3 significant figures, then this step results in 1.25. For example, if we want to round 1.2459 to 3 significant figures, then this step results in 1.25.

  5. Odds ratio - Wikipedia

    en.wikipedia.org/wiki/Odds_ratio

    Thus, when the probability of X occurring in group B is greater than the probability of X occurring in group A, the odds ratio is greater than 1, and the log odds ratio is greater than 0. Suppose that in a sample of 100 men, 90 drank wine in the previous week (so 10 did not), while in a sample of 80 women only 20 drank wine in the same period ...

  6. Viscosity - Wikipedia

    en.wikipedia.org/wiki/Viscosity

    Viscosity is a measure of a fluid's rate-dependent resistance to a change in shape or to movement of its neighboring portions relative to one another. [1] For liquids, it corresponds to the informal concept of thickness; for example, syrup has a higher viscosity than water. [2]

  7. Chi-squared distribution - Wikipedia

    en.wikipedia.org/wiki/Chi-squared_distribution

    Ramsey shows that the exact binomial test is always more powerful than the normal approximation. [9] Lancaster shows the connections among the binomial, normal, and chi-squared distributions, as follows. [10] De Moivre and Laplace established that a binomial distribution could be approximated by a normal distribution.

  8. Repeating decimal - Wikipedia

    en.wikipedia.org/wiki/Repeating_decimal

    The repeating sequence of digits is called "repetend" which has a certain length greater than 0, also called "period". [5] In base 10, a fraction has a repeating decimal if and only if in lowest terms, its denominator has any prime factors besides 2 or 5, or in other words, cannot be expressed as 2 m 5 n, where m and n are non-negative integers.

  9. Friction - Wikipedia

    en.wikipedia.org/wiki/Friction

    Coefficients of friction range from near zero to greater than one. The coefficient of friction between two surfaces of similar metals is greater than that between two surfaces of different metals; for example, brass has a higher coefficient of friction when moved against brass, but less if moved against steel or aluminum. [32]