Question

An educational psychologist wishes to know the mean number of words a third grader can read per minute. She wants to make an estimate at the 80% level of confidence. For a sample of 870 third graders, the mean words per minute read was 37.6. Assume a population standard deviation of 5.5. Construct the confidence interval for the mean number of words a third grader can read per minute. Round your answers to one decimal place.

Find lower and upper endpoint

Answer 1

We have given that,              
              
Sample mean =37.6      
Population standard deviation=5.5  
Sample size=870      
Level of significance =1-0.80=0.2      
Z critical value (by using Z table)=1.282      
              
  

          
Lower confidence limit =37.4
Upper confidence limit =37.8