Higher Engineering Mathematics

566 STATISTICS AND PROBABILITY

2. A frequency distribution of the class mid-
   point values of the breaking loads for 275
   similar fibres is as shown below:

Load (kN) 17 19 21 23 25 27 29 31

Frequency 9 23 55 78 64 28 14 4

Use normal probability paper to show that

this distribution is approximately normally

distributed and determine the mean and stan-

dard deviation of the distribution (a) from the

graph and (b) by calculation.

[

(a)x= 23 .5 kN, σ= 2 .9kN

(b)x= 23 .364 kN, σ= 2 .917 kN

]