In a study of differences in levels of community demand for firefighters, the following sample regression was obtained, based on data from 39 towns in Maryland:

where
y = number of full@time firefighters per capita
x1 = maximum base salary of firefighters, in thousands of dollars
x2 = percentage of population
x3 = estimated per capita income, in thousands of dollars
x4 = population density
x5 = amount of intergovernmental grants per capita, in thousands of dollars
x6 = number of miles from the regional city
x7 = percentage of the population that is male and between 12 and 21 years of age The numbers in parentheses under the coefficients are the estimated coefficient standard errors.
a. Find and interpret a 99% confidence interval for b5.
b. Test, against a two-sided alternative, the null hypothesis that b4 is 0, and interpret your result.
c. Test, against a two-sided alternative, the null hypothesis that b7 is 0, and interpret your result.

Transcribed Image Text:

y0.00232 0.00024 0.00002r2 + 0.00034r (000012) (0.00010) (0.000018) + 0.481 22x4 + 0.04950X5-0.0001 0x6 + 0.00645x7 (077954) (0.01172) (0.00005) 0.00306) R2 = 0.3572