Answer:
0.0228 = 2.28% probability that a one-month old girl will be categorized as having microcephaly
Step-by-step explanation:
Normal Probability Distribution
Problems of normal distributions can be solved using the z-score formula.
In a set with mean and standard deviation
, the z-score of a measure X is given by:
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.
Medscape defines microcephaly (small head syndrome) as a head circumference that is more than two standard deviations below the mean. What is the probability that a one-month old girl will be categorized as having microcephaly?
Probability of a z-score of -2 or less, which is the p-value of Z = -2.
Looking at the z-table, Z = -2 has a p-value of 0.0228.
0.0228 = 2.28% probability that a one-month old girl will be categorized as having microcephaly