Measures of central tendency:
Mode: The value or category that occurs with the highest frequency in a data set or distribution (the peak of the frequency curve).
Mean: The arithmetic average calculated by dividing the sum of all values by the total count.
Median: The central positional value that divides an ordered data set into two equal halves.
Range: The difference between maximum and minimum values.

Hydrostatic pressure equation:
In a static fluid of uniform density

\(\rho\), the hydrostatic pressure exerted at a vertical depth \(h\) below the free surface is given by the fundamental hydrostatic equation: \[P = \rho g h = \gamma h\]

where:

• \(\rho\) = fluid mass density (\(\text{kg/m}^3\))
• \(g\) = acceleration due to gravity (\(9.81\text{ m/s}^2\)) - \(h\) = fluid depth / head (m) - \(\gamma = \rho g\) = specific weight of fluid (\(\text{N/m}^3\))

Relationships between Total Product (TP) and Marginal Product (MP) in production economics:
(A) When MP is maximum -> (III) Inflection point of total product curve: The slope of the TP curve is maximum at its inflection point; beyond this point, TP switches from convex to concave.
(B) When MP is zero -> (I) Total product is maximum: When the slope of TP is zero (\(d(TP)/dX = 0\)), total physical product attains its peak.
(C) When MP decreases (positive and falling) -> (IV) Total product increases at decreasing rate: Law of diminishing returns operates; each additional unit of input adds less output than preceding units.
(D) When MP is constant -> (II) Total product increases at constant rate: The TP curve is a straight linear line with constant slope.