question 20

The average time spent sleeping (in hours) for a group of medical residents at a hospital can be approximated by a normal distribution, as shown in the graph to the right. Answer parts (a) and (b) below.

234567891011 SleepingTimesof MedicalResidents =6.4hours =1.3hour

(a) What is the shortest time spent sleeping that would still place a resident in the top 5% of sleeping times? Residents who get at least____

hours of sleep are in the top 5% of sleeping times.(Round to two decimal places as needed.)

(b) Between what two values does the middle 50% of the sleep times lie? The middle 50% of sleep times lies between ____

hours on the low end and

_______ hours on the high end.(Round to two decimal places as needed.)

question 21

The mean length of a human pregnancy is

270

days, with a standard deviation of

10

days. Use the empirical rule to determine the percentage of women whose pregnancies are between

260

and

280

days. (Assume the data set has a bell-shaped distribution.)

question 23

Find the equation of the regression line for the given data. Then construct a scatter plot of the data and draw the regression line. (The pair of variables have a significant correlation.) Then use the regression equation to predict the value of y for each of the given x-values, if meaningful. The table below shows the heights (in feet) and the number of stories of six notable buildings in a city.

Height,x	775	619	519	508	491	474		(a) x=502 feet	(b) x=644 feet
Stories, y	53	47	44	43	38	36		(c) x=310 feet	(d) x=734 feet

a.Find the regression equation

b. graph it.

c. Predict the value of y for x=502.

d.Predict the value of y for

x=644.

e. Predict the value of y for

x=310

f. Predict the value of y for

x=734.