(a)
To explain is the graduation rate among the VLBW group significantly lower than for the normal birth weight controls.
(a)

Answer to Problem 25.16CRE
Yes, the graduation rate among the VLBW group is significantly lower than for the normal birth weight controls.
Explanation of Solution
In the question, it is given that a long-term study followed very low birth weight babies (VBLW) to age twenty along with a control group of normal birth weight babies from the same population. Thus,
Thus, to do the mechanics of a hypothesis test for equality of population proportions we will use the calculator
Thus, by using the calculator
As we know that if the P-value is less than or equal to the significance level then the null hypothesis is rejected, so we have,
Thus, we have sufficient evidence to conclude that the graduation rate among the VLBW group is significantly lower than for the normal birth weight controls.
(b)
To explain is there good evidence that
(b)

Answer to Problem 25.16CRE
Yes, there is good evidence that mean IQ is lower among VLBW men than among controls from similar background.
Explanation of Solution
In the question, it is given that a long-term study followed very low birth weight babies (VBLW) to age twenty along with a control group of normal birth weight babies from the same population. Thus, we have,
VLBW | Control | |
Mean | 87.6 | 94.7 |
S.D. | 15.1 | 14.9 |
n | 113 | 106 |
Thus, for testing the hypothesis we will use the calculator
Thus, by using the calculator
As we know that if the P-value is less than or equal to the significance level then the null hypothesis is rejected, so we have,
Thus, we have sufficient evidence to conclude thatmean IQ is lower among VLBW men than among controls from similar background.
(c)
To compute a
(c)

Answer to Problem 25.16CRE
We are
Explanation of Solution
In the question, it is given that a long-term study followed very low birth weight babies (VBLW) to age twenty along with a control group of normal birth weight babies from the same population. Thus, we have,
VLBD women | Control | |
Mean | 86.2 | 89.8 |
S.D. | 13.4 | 14 |
n | 123 | 125 |
Thus, to find the confidence interval for mean we will use the calculator
Thus, we can conclude form this interval that we are
(d)
To explain can we conclude from this study that being born with a very low weight causes lower IQ and lower graduation rates by age twenty.
(d)

Answer to Problem 25.16CRE
Yes, we can conclude from this study that being born with a very low weight causes lower IQ and lower graduation rates by age twenty.
Explanation of Solution
In the question, it is given that a long-term study followed very low birth weight babies (VBLW) to age twenty along with a control group of normal birth weight babies from the same population. From part (a), we have sufficient evidence to conclude that the graduation rate among the VLBW group is significantly lower than for the normal birth weight controls. And from part (b), we have sufficient evidence to conclude that mean IQ is lower among VLBW men than among controls from similar background. And even in part (c), the confidence interval shows the lower IQ scores. Thus, we can conclude from this study that being born with a very low weight causes lower IQ and lower graduation rates by age twenty
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Chapter 25 Solutions
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