Chapter 27, Problem 34E

a)

To determine

To explain whether the association would appear to be weaker, stronger or the same if data had been plotted for individual babies instead of using monthly averages.

Answer to Problem 34E

The association would appear to be weaker if data had been plotted for individual babies instead of using monthly averages because the variation is more in individual than averages.

Explanation of Solution

Given:

  

The association would appear to be weaker if data had been plotted for individual babies instead of using monthly averages because the variation is more in individual than averages. Therefore, if the variation increases then the association will become weaker.

b)

To determine

To test an appropriate hypothesis.

Answer to Problem 34E

There is sufficient evidence to support a claim that there is an association between Temperature and Crawling Age.

Explanation of Solution

Given:

  

The null and alternative hypotheses:

  $\begin{array}{l}{H}_0:{\beta }_1=0\\ H_a:{\beta }_1\ne 0\end{array}$

Using excel,

  

Test statistic:

t = -3.237

Therefore, p-value would be,

P-value = .00890

Decision: P-value < 0.05, reject H₀.

Conclusion: There is sufficient evidence to support a claim that there is an association between Temperature and Crawling Age.

c)

To determine

To find the 95% confidence interval for the slope of the regression line.

Answer to Problem 34E

We are 95% confident that the slope of the population of regression line is between -0.1344 and -0.0248.

Explanation of Solution

Given:

  

Using excel,

  

Therefore, we are 95% confident that the slope of the population of regression line is between -0.1344 and -0.0248.