A 95% confidence interval has the following properties:

a) It allows the investigator to be 95% certain the estimate s/he obtained is the true estimate

b) The level of confidence has been established by a commission of experts and deviation from this 95% level requires written permission from your department chair

c) Confidence intervals convey the level of systematic error present in your study

d) It allows the investigator to be certain s/he will obtain the correct answer 95 times out of 100

e) None of the above