The probability is 0.69.
We find the z-scores that correspond with each end of the range we're looking for. To find a z-score, we use the formula:
Using a z-table (http://www.z-table.com) we see that the area under the curve left of the score 350 would be 0.228. The area under the curve left of the score 400 would be 0.918. To find just the range between 350 and 400, we subtract the area left of 350 from the area left of 400; this will give us just from 350 to 400:
0.918-0.228 = 0.69.
We find the z-scores that correspond with each end of the range we're looking for. To find a z-score, we use the formula:
Using a z-table (http://www.z-table.com) we see that the area under the curve left of the score 350 would be 0.228. The area under the curve left of the score 400 would be 0.918. To find just the range between 350 and 400, we subtract the area left of 350 from the area left of 400; this will give us just from 350 to 400:
0.918-0.228 = 0.69.