In a study of air quality in New York City, researchers collected data over 153 consecutive days between May and September 1973

In a study of air quality in New York City, researchers collected data over 153 consecutive days between May and September 1973. The response of interest is the measurements of ozone level, in parts per billion particles. Three independent variables were

considered:

• Solar radiation (Langleys) from 8:00am to noon at Central Park;

• Average wind speed (mph) from 7:00am to 10:00am at LaGuardia Airport;

• Daily maximum temperature (degrees Fahrenheit) at LaGuardia Airport.

The R output for regressing Ozone onto the three independent variables is given below.

Coefficients:

Estimate Std.    Error                   t value               Pr(>|t|)

(Intercept)         -64.34208          23.05472            -2.791                 0.00623 **

Solar.R                0.05982              0.02319              2.580                    0.01124 *

Wind                   -3.33359              0.65441              -5.094                1.52e-06 ***

Temp                  1.65209              0.25353               6.516                  2.42e-09 ***

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Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

(a) Find the slope term associated with each of the three independent variables and

interpret. Which one(s) are positively correlated with ozone level, and which

one(s) are negatively correlated with ozone level?

(b) Under significance level of α = 0.01, which independent variable(s) are insignificant?

(c) The record for Sept. 27, 1973 is given below.

Ozone  Solar.R  Wind   Temp     Month Day

NA        145       13.2       77        9             27

The ozone level is shown as "NA", a symbol for missing data. Based on the

measurements for solar radiation, wind speed, and temperature on that day, what

is the predicted ozone level?