Problem #1:

Estimate the minimum sample size required to estimate the proportion of 
modules in a portfolio that are Y2K compliant to an accuracy of 0.05 with 
95% confidence.

Solution:

Since an estimate of pi is not provided then a conservative estimate may
be obtained if we let p=0.5. You know from CI theory that the plus/minus
amount for a 95% CI is: 
        z(95)*sqrt(pi*(1-pi)/n) 
Since z(95) is 1.95 and the required accuracy is 0.05 then:
	0.05=1.95*sqrt(0.5*0.5/n)
Rearranging terms:
	n=(1.95**2)*(0.5*0.5)/0.05**2=380.25

Hence 381 programs would be a conservative estimate of the number of 
programs required.

Problem #2:

Assume that for other companies like yours 75% of programs are Y2K compliant. 
Use this fact in estimating the sample size.

Solution:

In this case it is reasonable to use 0.75 as an estimate for pi. The working 
is the same as #2 above:
	0.05=1.95*sqrt(0.75*0.25/n)
Rearranging terms:
	n=(1.95**2)*(0.75*0.25)/0.05**2=285.19

Hence 286 programs would be the number of programs required.