You plan to conduct a survey to find what proportion of the

You plan to conduct a survey to find what proportion of the workforce has two or more jobs. You decide on the 90 percent confidence level and state that the estimated proportion must be within 3 percent of the population proportion. A pilot survey reveals that 7 of the 50 sampled hold two or more jobs.

How many in the workforce should be interviewed to meet your requirements? (Round up your answer to the next whole number.)

  Number of persons to be interviewed: _______.

Solution

You plan to conduct a survey to find what proportion of the workforce has two or more jobs. You decide on the 90 percent confidence level and state that the estimated proportion must be within 3 percent of the population proportion. A pilot survey reveals that 7 of the 50 sampled hold two or more jobs.

How many in the workforce should be interviewed to meet your requirements? (Round up your answer to the next whole number.)

  Number of persons to be interviewed: _____

P=7/50=0.14

For 90%, z=1.645

d=0.03

Sample size = (z²*p*(1-p))/d²

= (1.645²*0.14*0.86)/0.03²

=362.006

The sample size required= 363

( This is manual calculation. some software gives 362 as the final answer because they use z value as 1.64485362695147)