The proportion of public accountants who have changed compan

The proportion of public accountants who have changed companies within the last three years is to be estimated within 4%. The 90% level of confidence is to be used. A study conducted several years ago revealed that the percent of public accountants changing companies within three years was 22.

How many public accountants should be contacted if no previous estimates of the population proportion are available?

Solution

a)
Compute Sample Size ( n ) = n=(Z/E)^2*p*(1-p)
Z a/2 at 0.1 is = 1.64
Samle Proportion = 0.22
ME = 0.04
n = ( 1.64 / 0.04 )^2 * 0.22*0.78
= 288.46 ~ 289

b)
Compute Sample Size ( n ) = n=(Z/E)^2*p*(1-p)
Z a/2 at 0.1 is = 1.64
Samle Proportion = 0.5
ME = 0.04
n = ( 1.64 / 0.04 )^2 * 0.5*0.5
= 420.25 ~ 421