Posted by Jessica on .
A random sample of 50 students has a test score average with a standard deviation of 10.9. Find
the margin of error if c = 0.90.

Statistics 
MathGuru,
Margin of error = + or  1.645 (sd/√n)
Substitute the values given and determine the margin of error.
(The value of 1.645 was found using a ztable for 90% confidence.)
I hope this helps.