Answer: 10 customers.
Step-by-step explanation:
The formula to find the required sample size :
[tex]n=p(1-p)(\dfrac z^*}{E})^2[/tex] (1)
, where p= prior population proportion.
n= sample size.
[tex]\sigma[/tex] = Population standard deviation from previous studies.
Let p be prior population proportion of the customers who click on ads on their smartphones .
As per given , we have
p=0.62
E= 0.27
For 92% confidence , significance level : [tex]\alpha=1-0.92=0.08[/tex]
The critical value of z for 92% confidence interval from z-table would be
[tex]z_{\alpha/2}=z_{0.04}=1.75[/tex]
Put theses values in the formula (1), we will get
[tex]n=(0.62)(1-0.62)(\dfrac{(1.75)}{0.27})^2[/tex]
[tex]n=(0.2356)(6.48148)^2= 9.89745775254\approx 10[/tex]
Therefore , the company should survey 10 customers .
