Margin of error & confidence interval of pop. Mean with large sample

Question

how can I find the margin error & confidence interval for population mean with sample = 138, mean=64 abs standard deviation = 4

confidence level = 90%

Answer 1

In a nutshell:

Confidence Interval = sample mean plus/minus margin of error

= sample mean +/- confidence level value * standev / squareroot(sample size)

Find your confidence level value (either a z or a t) from sample size, type of test, and confidence level 90%.

Then plug in.