thesIt » basic

If we assume a normally distributed popu …

Arif — Sun, 22 Aug 2010 12:19:08 +0000

If we assume a normally distributed population with mean μ and standard deviation σ, and take sample

statistical error is then

Residual

while residual is

hat over the letter ε indicates an observable estimate of an unobservable quantity called ε.

Boxplot drawing

Arif — Sun, 22 Aug 2010 07:29:29 +0000

Drawing boxplot from the following data, whiskers are determined from 1.5 IQR

no	datum	drawn as
1	0.026	outlier
2	0.048	whisker low
3	0.070	Q1
4	0.072
5	0.076	Q2
6	0.084
7	0.086
8	0.099	Q3
9	0.102
10	0.103	whisker high

Outlier

0.026 becomes outlier because 1.5IQR boundary (IQR = Q3 – Q1 = 0.02908) for the lower boundary is Q1 -1.5IQR = 0.0404, hence whisker is 0.048 which is more close to the box inside making 0.026 outlier.

boxplot-basic-concept-example.png

Viscosity is a measure of the resistance …

Arif — Sun, 22 Aug 2010 06:43:00 +0000

Viscosity is a measure of the resistance of a fluid which is being deformed by either shear stress or tensile stress.

The cgs physical unit for dynamic viscosity is the poise (P), more commonly expressed, particularly in ASTM standards, as centipoise (cP)

Density of a material is defined as its …

Arif — Sun, 22 Aug 2010 06:32:12 +0000

Density of a material is defined as its mass per unit volume.
ρ (in some countries i.e. USA) is also defined as weight per unit volume
Units: (kg/m³), g/cm³

Easiest description standard deviation

Arif — Mon, 28 Jun 2010 22:27:38 +0000

Easiest description for standard deviation definition is distance from mean (expected value) as shown in this graphical depiction

where all the values fall at σ distance within the dotted circle radius. Of course a more real-life situation is shown as

where σ is the square root of the following mean

σ² a.k.a. variance is averaged quadratic distances. Explanation:

Distance may have several concepts, in this variance description, distance shows “how far” a value is from its population expected value (mean). Quadratic form of this “how far” is

pH is a measure of the acidity or basici …

Arif — Sat, 27 Feb 2010 10:56:17 +0000

pH is a measure of the acidity or basicity of a solution, defined as minus the decimal logarithm of the hydrogen ion activity in a solution.

common pH scale (can't find where water is?)

Viscosity is a measure of the resistance …

Arif — Sun, 21 Feb 2010 12:39:21 +0000

Viscosity is a measure of the resistance of a fluid which is being deformed by either shear stress or tensional stress. In everyday terms (and for fluids only), viscosity is “thickness”. Thus, water is “thin”, having a lower viscosity, while honey is “thick”, having a higher viscosity.

Viscosity describes a fluid’s internal resistance to flow and may be thought of as a measure of fluid friction. See Newton’ expression: the constant μ is known as the coefficient of viscosity, the viscosity, the dynamic viscosity, or the Newtonian viscosity.

Verification: Is the product being built …

Arif — Sat, 20 Feb 2010 14:30:46 +0000

Verification: Is the product being built right?
Validation: Is the right product being built?

Spinning drop method (rotating drop meth …

Arif — Fri, 19 Feb 2010 11:49:55 +0000

Spinning drop method (rotating drop method) is one of the methods that is used to measure interfacial tension. Basically, measurements are carried out in a rotating horizontal tube which contains a dense fluid. One drop of a less dense liquid is placed inside the fluid.

Since the rotation of the horizontal tube creates a centrifugal force towards the tube walls, the liquid drop starts to be elongated and this elongation stops when the interfacial tension and centrifugal forces are balanced. Values obtained at this equilibrium point are used to estimate surface tension of the particular liquid by using appropriate correlations. A device called “spinning drop tensiometer” is generally utilized for this purpose.

radius of curvature of a curve at a poin …

Arif — Wed, 17 Feb 2010 05:22:45 +0000

osculating circle

radius of curvature of a curve at a point is the radius of the osculating circle at that point.