To study bonding between mothers and infants, a researcher places each mother an

Question

To study bonding between mothers and infants, a researcher places each mother and her infant in a playroom and has the mother leave for 10 minutes. The researcher records crying time in the sample of infants during this time that the mother was not present and finds that crying time is normally distributed with M = 7 and SD = 1.1. Based on the empirical rule, state the range of crying times within 68% of infants cried, 95% of infants cried, and 99.7% of infants cried. (a) 68% of infants cried to min (b) 95% of infants cried to min (c) 99.7% of infants cried to min

Explanation / Answer

Mean is 7 and s is 1.1

a) For 68% z is 1 using empirical rule, thus the lower limit is mean-z*s =7-1*1.1=5.9 and the upper limit is mean+z*s= 7+1*1.1=8.1

b) For 95% z is 2 , thus lower limit is 7-2*1.1=4.8 and upper limit is 7+2*1.1=9.2

c) For 99.7%, z is 3 thus lower limit is 7-3*1.1=3.7 and upper limit is 7+3*1.1=10.3

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