If 40 of the moms working in Yahoo favor remote working what

If 40% of the moms working in Yahoo favor remote working, what sample size should we choose to be 95% sure that at least 20 moms favor remote working within the chosen sample?

a) 66

b) 80

c) 68

d) 67

Solution

proportion of moms working in Yahoo favour remote working =40% = 0.4

If atleast 20moms favour means

40:100 = 20:n where n is the sample size

Or 40n =2000

n >=50

For 95% sure we make adjustments as 1.96 sigma

50+1.96(0.4898)/10

Approximately 66 is the answer.