In a certain country, the average age is 31 years old and the standard deviation is 4 years. If we select a simple random sample of 100 people from this country, what is the probability that the average age of our sample is at least 32?
0.006
0.599
0.401
0.994
Solution :
Given that ,
mean = = 31
standard deviation = = 4
n = 100
= 31
= / n = 4 / 100 = 0.4
P( ) = 1 - P( < 32)
= 1 - P[( - ) / < (32 - 31) / 0.4]
= 1 - P(z < 2.5)
= 0.006
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