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 
False
true
false
false
Mark brainliest please
Answer:
X=5
Step-by-step explanation:
f(1)= -1^2+4(1)+12=15
f(2)= -2^2+4(2)+12=16
f(3)= -3^2+4(3)+12=15
f(4)= -4^2+4(4)+12=12
f(5)= -5^2+4(5)+12=7
g(1)=1+2=3
g(2)=2+2=4
g(3)=3+2=5
g(4)=4+2=6
g(5)=5+2=7
so g(5)=f(5)= X=5
The value of 2a + 3b is 13