Avinash.tech(…)

Whats a Normal Curve ? 

What is Standard unit ?

A value is converted to Standard Units by seeing how many SD’s it is above or below the average. Lets take the following example to make it a bit clearer.

The average height for women age 18 and above was suppose 63.5 inches; the SD was 3 inches. One of these women was 69.5 inches tall. What was her height in standard units? Our subject was 6 inches taller than the average, and 6 inches is 2 SD’s. In standard units , her height is +2.

Calculating Standard Unit for a sample data:

X : 1 , 3 , 4 , 5 , 7 .

X in Standard Units = (X[i] – Average ) / SD , where i is the index in X. X[1] is 1 , X[2] is 3 and so on.

Average = 4 and SD = 2 ( How to calculate SD ).

X in Standard Units would be : -1.5 , -0.5 , 0 , 0.5 , 1.5 .

Sample calculation for X[1] = ( 1 – 4 ) / 2  = -1.5

Standard Units are very important to get the sample data set to fall in the same scale. Is also a  crucial part of calculating Correlation Coefficient ( r ) .