Birth weight and mother’s age

Topic: Regression examples · more questions on this topic
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For 74 babies whose mothers smoked, a fit of birth weight in grams on the mother’s age gives

\widehat{\mathrm{weight}}=3204.23-18.84\times\mathrm{age}.

The p-value for the slope is 0.1102.

1. Predict the mean birth weight at ages 15 and 35.

2. Is the slope distinguishable from zero at level 0.05?

Worked answer (click to show)

At age 15 the fitted mean is 3204.23-18.84\times 15=2921 g. At age 35 it is 3204.23-18.84\times 35=2544 g. The slope’s p-value is 0.1102, so the decrease is not distinguishable from zero at level 0.05.