Answer:
a) The mean is 
b) The standard deviation is 
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 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.
The probability a student selected at random takes at least 55.50 minutes to complete the examination equals 0.6915.
This means that when X = 55.5, Z has a pvalue of 1 - 0.6915 = 0.3085. This means that when 
So




The probability a student selected at random takes no more than 71.52 minutes to complete the examination equals 0.8997.
This means that when X = 71.52, Z has a pvalue of 0.8997. This means that when 
So




Since we also have that 





Question
The mean is 
The standard deviation is 
-2.8 • -2.8 • -2.8 • -2.8 • -2.8 • -2.8
=481.890
7= 16 lb >16 Oz 16x16=256
8= 1500 lb < 2T 2000+2000
9= 3T>5999 lb 2000x3
10= 1600 Oz > 10 lb 1600÷16=100
11= 19 lb>300 Oz 19x16=304oz
12= 8 oz= 1/2 lb 16 ounces = 1 pound 1/2=8
13= pounds=6000 tons= 1, 1.5
Answer:
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Step-by-step explanation: