Answer:
The proportion of children in this age range between 70 lbs and 85 lbs is of 0.9306.
Step-by-step explanation:
When the distribution is normal, we use the z-score formula.
In a set with mean and standard deviation
, the zscore 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 pvalue, we get the probability that the value of the measure is greater than X.
A study suggested that children between the ages of 6 and 11 in the US have an average weightof 74 lbs, with a standard deviation of 2.7 lbs.
This means that
What proportion of childrenin this age range between 70 lbs and 85 lbs.
This is the pvalue of Z when X = 85 subtracted by the pvalue of Z when X = 70. So
X = 85
has a pvalue of 1
X = 70
has a pvalue of 0.0694
1 - 0.0694 = 0.9306
The proportion of children in this age range between 70 lbs and 85 lbs is of 0.9306.