What proportion of robins have wingspans less than 12 inches?

Question

. The area to the left of 14 for a N(22,4) distribution converted to a standard normal distribution

           A) .0912

           B) .0228

           C) .2280

           D) .6340

     15. Robins are common birds in North America. Suppose that the wingspan of robins is approximately

            normal with mean 16 inches and standard deviation  3.5  inches. What proportion of robins have wingspans less than 12  inches? Report your answer with three decimal places.

           A) .721

           B) .127

           C) .873

           D) .999

Answer 1

Prob( x< 14) = Prob( z < (14-22)/4)

= Prob( z < -2)

= 0.022750132

Yes, I agree, the answer is B

----------------------

prob (x<12) = Prob(z < (12-16)/3.5)

= Prob(z < -1.1428571428571428571428571428571)

where

-4/3.5 = -4/1 divided by 7/2 = -4/1 * 2/7 = -8/7 = -(1+1/7)

Per the table the probability is 0.126548954...

Again, yes I agree, the answer is B