Question

You examine a small sample of 36 users of Snapchat. Your survey showed an average age of 25 years for Snapchat users. Assume the ages of all users has a normal distribution with a standard deviation of 1.8 years. The 98% confidence interval for the average age of all users is (use area of .0099 in each tail, .0100 is not given in the standard normal table):

a 24.385 to 25.615

b 23.200 to t 26.800

c 24.301 to 25.699

d 23.236 to 26.764

Answer 1

We have given that,              
              
Sample mean =25      
Population standard deviation=1.8  
Sample size=36      
Level of significance =1-0.98=0.02      
Z critical value (by using Z table)=2.326      
              
Confidence interval formula is              


=(24.301,25.699)

c 24.301 to 25.699