The arithmetic mean and standard deviation of a certain normal distribution are 15 and 1.5, respectively. What value is exactly 2 standard deviations less than the mean?	Choose the correct choice from the following answers:
A) 10.5 B) 11 C) 11.5 D) 12 E) 12.5
The value which isexactlytwo SD less than the mean is:mean-2*SD=15-2*1.5= 
<gadget id="calculator">15-2*1.5</gadget>
<output>12</output>
12.   Answer: 12.
<result>D</result>
The arithmetic mean and standard deviation of a certain normal distribution are 15 and 1.5, respectively. What value is exactly 2 standard deviations less than the mean?