David L. answered 04/27/20
Statistics Professor with PhD; Math, Statistics and R Tutor
When you conducted your survey, you calculated a sample proportion of people who said they spent more than 4 hours on their phones daily.
p* = 0.95
n = 40
The claim is that 75% of the population spends omre than 4 hours on their phone daily.
p0 = 0.75
The relative sample statistic for this scenario is given by the following:
z = [p* - p0] / (standard error)
standard error = √(p0*(1-p0)/n)
standard error = √(0.75*(1-0.75)/40) = 0.068465
z = [0.95 - 0.75] / 0.068465 = 2.921