Two hundred and eighty boys completed a test that measures the distance that the subject can walk on a flat, hard surface in 6 minutes. For each age group shown in the table, the median distance walked by the boys in that age group is also given.

Age Group	Representative Age (Midpoint of Age Group)	Median Six-Minute Walk Distance (meters)
3-5	4	544.3
6-8	7	584.0
9-11	10	667.3
12-15	13.5	701.1
16-18	17	727.6

This experiment also reported the 6-minute walk distances (in meters) for 248 girls age 3 to 18 years. The median 6-minute walk distances for girls for the five age groups, respectively, were

494.4

576.3

655.8

659.6

662.9.

Find the equation of the least-squares regression line that describes the relationship between median distance walked in6 minutesand representative age for girls. (Round your values to three decimal places.)

= + ()x

(d)Compute the five residuals. (Round your answers to three decimal places.)

Representative Age (x)	Residual (meters)
4
7
10
13.5
17

According to a research paper, the carbon monoxide exposure of someone riding a motorbike for 5 km on a highway in a particular city is approximately normally distributed with a mean of 18.6 ppm. Suppose that the standard deviation of carbon monoxide exposure is 5.3 ppm.

(a)Approximately what proportion of those who ride a motorbike for 5 km on a highway in this city will experience a carbon monoxide exposure of more than 20 ppm? (Round your answer to four decimal places.)

(b)Approximately what proportion of those who ride a motorbike for 5 km on a highway in this city will experience a carbon monoxide exposure of more than 25 ppm? (Round your answer to four decimal places.)