A sample of 15 test-tubes were tested for the number of times they can be heated on a Bunsen burner before they cracked. For the conclusion of this testing, the researcher stated, "I am 95% confident that the true number of times that a test-tube of this type can be used before it cracks is between 1200 and 1250 times."

What was the sample mean? (hint - what was the average of the 15 that they tested)

What is the margin of error? +/-