In a study on​ infants, one of the characteristics measured was head circumference. The mean head circumference of 13 infants was 34.3 centimeters​: a. Assuming that head circumferences for infants are normally distributed with standard deviation 2.4 ​cm, determine a 90​% confidence interval for the mean head circumference of all infants. The confidence interval for the mean head circumference of all infants is from enter your response here ____cm to____cm b. Obtain the margin of​ error, E, for the confidence interval you found in part​ (a). The margin of error is ____cm. ​ c. Explain the meaning of E in this context in terms of the accuracy of the estimate. Choose the correct answer below and fill in the answer box to complete your choice.