1. The mean life span of Americans is 79 years (2012, CDC) with a standard devia
ID: 3200543 • Letter: 1
Question
1. The mean life span of Americans is 79 years (2012, CDC) with a standard deviation 15 years (R.D> Edwards, NEBER, 2008). If we assume the histogram of life span is Normal.
a. What is the middle 68% range of Americans’ life span?
b. What is the middle 95% range of American’s life span?
c. How much percentage of American live more than 124 years approximately?
d. What can you say about the normal assumption?
2. Calculate the Z scores for observations for each data set.
Date set 1: 0 .03, 0.5, 0.6, .08, 1.3
Date Set 2: 30, 50, 60, 80, 130
Date set 3: 130, 150, 160, 180, 230
Explanation / Answer
As per chegg rules we are supposed to answer the first 4 questions.
1)Mean=79years,sd=15years
a)Middle 68%->Data within 1 Standard deviation of mean=(79-15,79+15)=(64years,94years)
b)Middle 95%->Data within 2 Standard deviation of mean=(79-2*15,79+2*15)=(49years,109years)
c)P(X>124)=P(Z>(124-79)/15=3)=P(Z>3)=0.00135=0.135%
d)I would say the normality assumption could be wrong. This is because we got a probability of .135%for the americans to live beyond 124years which is almost impossible.
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