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 
Answer:
12s
Step-by-step explanation:
5s + 7s = (5 + 7) s= 12s
This is your answer
Answer:81030m
Step-by-step explanation:1km=1000m, 81km=81000+30=81030m
Answer: 18x + 12
Step-by-step explanation:
3 ( 6x + 4 )
3 x 6x = 18x
3 x 4 = 12
18x + 12
<span>52 can be broken down to the following
2*26 =52
2*(2*13) <---13 x 2=26 x 2=52
2*2*13 or 2^2*13 <--BOTH mean the same thing :) </span><span>
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