the mean annual income for people in a certain city is 46 (thousands of dollars), with a standard deviation of 42. A pollster draws a sample of 60 people to interview. What is the probability that the sample mean income is less than 42 (thousands of dollars)?
Solution :
Given that ,
mean = = 46
standard deviation = = 42
_{} = / n = 42 / 60
P( < 42) = P(( - _{} ) / _{} < (42 - 46) / 42 / 60)
= P(z < -0.74)
= 0.2297
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