Answer: ± 1.96
Step-by-step explanation:
Given the following :
Mean (m) time spent = 11.85
Standard deviation = 4 minutes
Since the population of site visits is Normally distributed, Hence, the test statistic will follow a normal distribution :
The test the hypothesis that mean time has changed at 0.05 confidence interval
Normal distributions have a mean value of 0 and standard deviation of 1
Using a two tailed test At 0.05 confidence interval ;
Using the critical value calculator, which in general under normal distributions :
0.05% confidence interval for a two tailed test is
± 1.96