All you can get from this is an estimated range. You had 11 parts rejected out of a sample size of 100. You want a confidence of 90%, which means alpha = 10%. Since this is two sided, the z value is based on alpha/2. Z for 0.05 is 1.645. Do the math and the confidence limits range from 6.85% to 17.21%. So, that is the range for % rejects based on this one sample result and size.