Answer:
a) 279 b)254
Step-by-step explanation:
Mean = 269 days
standard deviation = 8 days
let n be the pregnancy lenght.
using normal distribution formula
z = (n – mean)/ standard deviation
n = z * standard deviation + mean
Now, z values for the top 12% has to be found using a z table.
The top 12% means 88% of area under the curve. In this case z = 1,176
n = 1,176 * 8 + 269
n = 278.4 = 279
The bottom 3% means 97% of area under the curve. In this case z = -1,882
n = -1,882 * 8 + 269
n = 253.94 = 254
