Question

consider

The temperature at any random location in a kiln used for manufacturing bricks is! Normally distributed with a mean of 1000°F and a standard deviation of 50°F. If bricks are fired at a temperature above 1125°F, they will crack and must be discarded. If the bricks are placed randomly throughout the kiln, what is the percentage of bricks that crack during the firing process? a) 0.62% b) 47.72% c) 49.38% d) 2.28%

Answer 1

we know that

Z = (X- MEAN)/SD

= (1125 -1000)/ 50

=125/50

=2.5

Required area = area to the right from (z=2.5)

= 1- area from left to z=2.5

= 1- 0.9938

= 0.0062

Percentage of bricks that crack during the firing process =100*0.0062

=0.62%   Answer

2. H0 : p = 0.47 vs Ha :  $p\neq 0.47$ for change two tailed test

change may be left or right so we use two tailed.