A Denver study looked at the relationship between climate and the age at which infants begin crawling [8]. (It was suspected that crawling is delayed when infants wear heavy clothing.) Tables 8.6 shows the average age (in weeks) when children born in different months began crawling and the average Denver temperature for the sixth month after birth.

a. Draw a scatter diagram and the least squares line.

b. What is your dependent variable? Explain your reasoning.

c. Is the estimated slope statistically significant at the 5 percent level?

d. Is the sign of the estimated slope consistent with the researchers’ theory?

e. Is the value of the estimated slope plausible?

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Crawling Age Temperature Crawling Age Temperature January 29.84 66 July 33.64 33 February 30.52 73 August 32.82 30 March 29.70 72 September 33.83 33 April 31.84 63 October 33.35 37 May 28.58 52 November 33.38 48 June 31.44 39 December 32.32 57