Answer:
0.3811 = 38.11% probability that he weighs between 170 and 220 pounds.
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.
In this question, we have that:
Find the probability that he weighs between 170 and 220 pounds.
This is the pvalue of Z when X = 220 subtracted by the pvalue of Z when X = 170.
X = 220
has a pvalue of 0.6554
X = 170
has a pvalue of 0.2743
0.6554 - 0.2743 = 0.3811
0.3811 = 38.11% probability that he weighs between 170 and 220 pounds.