Short Essay on Median and Mode (409 Words)

Here is your Short Essay on Median and Mode !

The Median:

The median (M) is a statistics of location occasionally useful m biological research. It is defined as that value of the variable (in an ordered array) that has an equal number of items on either side of it. Thus, the median divides a frequency distribution into two halves. In the following sample of five measurements,

14, 15, 16, 19, 23

M = 16, since the third observation has an equal number of obser­vations on both sides of it. We can visualize the median easily if we think of an array from largest to smallest – for example a row of men lined up by their heights. The median individual will then be that person having an equal number of men on his right and left sides.

His height will be the median height of the sample considered. This quantity is easily evaluated from a sample array with an odd number of individuals. When the number in the sample is even, the median is conventionally calculated as the midpoint between the (n/2) th and the [(n/2) + 1] th variate. Thus, for the sample of four measurements,

14, 15, 16, 19

the median would be the midpoint between the second and third items, or 15.5.

Median has wide application in behaviour biology, pollution (i.e., the median lethal or effective dose, LD₅₀ or ED₅₀) and mutation (the median time for a mutation to appear in a number of lines of species).

The Mode:

The mode refers to the most “fashionable” value of the vari­able in a frequency distribution, or the value represented by the greatest number of individuals. For example, the number of tillers per plant in a sample of ten plants were—10, 9, 10, 11, 9, 12, 10, 10, 9, 12 and the arithmetic mean (x, read as x bar) and mode of the numbers of tillers per plant can be calculated as follows:

x = Ʃ x/ 10,

= (10+9+10+11+9+12+10+10+9+12) / 10

= 10.2

In this sample 9 occurs three times, 10 four times, 11 once and 12 twice. Thus 10 is the mode.

When seen on a frequency distribution, mode is the value of the variable at which the curve peaks. In biology mode does not have many applications.

Distributions having two peaks (equal or unequal in height) are called bimodal; those with more than two peaks are multimodal. In U-shaped distribution, the low point at the middle of the distribution as an antimode.