请问

问题如下：

Dennehy believe that the number of defective assemblies per hour is a function of the outside air temperature and the speed (production rate) of the assembly lines.

Using the data provided in Exhibit 1, Dennehy tests the hypothesis that the coefficients for outside air temperature and assembly line speed are significantly different from zero, using a significance level of 5%.

Based on Exhibit 1 and statistical tests, the best conclusion Dennehy can make is that the regression coefficient is significantly different from zero with respect to the coefficient(s) for:

选项：

A.

assembly line speed (b₂) only.

B.

outside air temperature (b₁) only.

C.

both outside air temperature (b₁) and assembly line speed (b₂).

解释：

The null hypotheses are that the coefficients equal zero. The alternative hypotheses are that the coefficients do not equal zero (two-tailed tests). The appropriate test statistics, t, are calculated by dividing the estimates of the coefficients by their respective standard error.

t_b1 = 0.0006/0.0010 = 0.60

t_b2 = 0.5984/0.30 = 1.9947

The test statistic for outside air temperature is less than the critical value of 1.96. The test statistic for assembly line speed exceeds the critical value of 1.96. Dennehy cannot reject the null hypothesis that the population regression coefficient for outside air temperature,b₁, is zero. Dennehy can reject the null hypothesis that b₂ is zero at the 5% level of significance.