Since it is two-tailed, find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability (.05 rather than .10) and insert its Z score in the equation below.
90% = mean ± 1.645 SEm
SEm = SD/√n
The standard deviation of test scores on a certain achievement test
Is 11.3. If a random sample of 81 students had a sample score of 74.6 , find a 90% confidence interval
estimate for the average score of all students.
1 answer
1 answer