We are going to run the following problem using STORM Software. A random sample
ID: 362729 • Letter: W
Question
We are going to run the following problem using STORM Software.
A random sample of 7 one baby live births revealed the following birth weights (lbs) and cigarette smoking habits of mothers (cigarettes smoked per day:
Cigarettes/day 0 10 0 30 0 25 40
Baby Birth Weight 8.5 6.5 7.2 5.8 8.0 8.3 6.0
Run a simple linear regression on the above data.
(a) What is the estimated regression line?
(b) What sort of relationship exists between the birth weight of the smoking habit of the mother
(c) Interpret the intercept and the slope of the regression line.
(d) Interpret the R-Square value.
(e) In your opinion, what other variables not in this regression have a bearing on the birth weight of babies?
(f) Predict the average birth weight of a baby (i) of a non-smoking mother, (ii) a mother with a one-pack-a-day habit, (iii) a mother with a two-pack a day habit, (iv) a mother with a three pack-a-day habit, (v) a mother with a five-pack-a-day habit. Which of the above predictions are you least sure of and why?
Explanation / Answer
The output of the simple regression using excel is as follows :
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a) The estimated regression line
y = 7.9769 - 0.0443 x
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b) A linear relationship exists between the birth weight and the smoking habit of the mother.
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c) The intercept is y = 7.9769 which is the value of y when x = 0
The slope is -0.0443. Negative slope indicates that y the dependent variable decreases when x the independent variable increases.
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d) For a simple linear regression, the term r2 is known as the coefficient of determination. The r2 can be interpreted as the proportion of the variance in y attributable to the variance in x .
In the output, the value of r2 equals 0.36809 which indicates that the correlation between the dependent variable (y)and the indepenent variable x is of less significance.
Ciggarates per day Baby weight 10 8.5 20 6.5 0 7.2 30 5.8 0 8 25 8.3 40 6Related Questions
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