Use of normal distribution as an approximation to poisson distribution.

This problem have been taken from the old paper of 'MASTER OF BUSINESS ADMINISTRATION'

Examination with little modifications

A complex plasma television component has 1000 joints soldered by a machine which is known to produce on average one defective in forty. The components are examined and faulty solderings are corrected by hand. If components requiring more than 35 corrections are discarded, what proportion of components will be thrown away?

Answer:-

Let 'n' be the number of joints and 'p' the probability of defective joints required to be corrected by hand.

Mean=1000*0.025=25

and

S.D.=5

Using normal approximation to the Poisson distribution

$\displaystyle \frac{35-25}{5}=2$

Using normal tables,we get

0.5-0.4773=0.0227

Hence we conclude that 2.27% of the components will be thrown away.

This answer is required to be verified. Answer is not available in the paper set.

If answer is wrong, reply me.

Re: Use of normal distribution as an approximation to poisson distribution.

Your workings look correct but don't you mean "Using normal approximation to the Binomial distribution" ?