Crawling Researchers at the University of Denver Infant Study Center $R ^ { 2 }$

question 53

Essay

Crawling Researchers at the University of Denver Infant Study Center investigated
whether babies take longer to learn to crawl in cold months (when they are often bundled
in clothes that restrict their movement) than in warmer months. The study sought an
association between babies' first crawling age (in weeks) and the average temperature
during the month they first try to crawl (about 6 months after birth). Between 1988 and
1991 parents reported the birth month and age at which their child was first able to creep
or crawl a distance of four feet in one minute. Data were collected on 208 boys and 206
girls. The graph below plots average crawling ages (in weeks) against the mean
temperatures when the babies were 6 months old. The researchers found a correlation of r
= -0.70 and their line of best fit was
a. Draw the line of best fit on the graph. (Show your method clearly.)
b. Describe the association in context.
c. Explain (in context) what the slope of the line means.
d. Explain (in context) what the y-intercept of the line means.
e. Explain (in context) what $R ^ { 2 }$
means.
f. In this context, what does a negative residual indicate?

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Definitions:

Late 1820s

A period marked by political and social changes in the United States, including the early stages of the Jacksonian democracy and increasing tensions over slavery.

Publication

Publication involves making content available to the public, typically through printed works like books and magazines, or digital forms such as blogs and online articles.

Andrew Jackson

The seventh President of the United States (1829-1837), known for his populist approach, founding the Democratic Party, and policies leading to the Trail of Tears.