At what age do babies learn to crawl? Does it take longer to learn in the winter, when babies are often bundled in clothes that restrict their movement? Perhaps there might even be an association between babies’ crawling age and the average temperature during the month they first try to crawl (around 6 months after birth). Data were collected from parents who brought their babies to the University of Denver Infant Study Center to participate in one of a number of studies. Parents reported the birth month and the age at which their child was first able to creep or crawl a distance of 4 feet within one minute. Information was obtained on 414 infants (208 boys and 206 girls). Crawling age is given in weeks, and average temperature (in degrees Fahrenheit) is given for the month that is 6 months after the birth month.

a. Make an appropriate graph to display the relationship between average temperature and average crawling age. Describe what you see. Some computer output from a least-squares regression analysis of the data is shown.

b. What is the equation of the least-squares regression line that describes the relationship between average temperature and average crawling age? Define any variables that you use.

c. Interpret the slope of the regression line.

d. Can we conclude that warmer temperatures 6 months after babies are born causes them to crawl sooner? Justify your answer.

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Birth month Average crawling age Average temperature January 29.84 66 February 30.52 73 March 29.70 72 April 31.84 63 Мay 28.58 52 June 31.44 39 July 33.64 33 August 32.82 30 September 33.83 33 October 33.35 37 November 33.38 48 December 32.32 57