Question 423:

Asked on September 28, 2008

Tags: Z-Score

1

Answer:

No answer provided yet.

We'd calculate the z-score for this event, then find the probability for this normal score. To get a z-score, subtract the data-point from the mean and divide that result by the standard deviation.

1. So (300-268)/15 = a z-score of 2.133.
2. Now we lookup the area under the normal curve up to 2.133 standard units using the z-score to percentile calculator.  Select 1-sided area and you should get 98.35%.

So the probability a pregnancy lasts 300 days or longer is equal to 100-98.35 = 1.65%--not very many.

See also question 401