= Solution
The null hypothesis is
$$
H_0:\beta_{\rm type2}=\beta_{\rm type3}
=\beta_{\rm posout}=0,
$$
against the alternative that at least one coefficient is nonzero. The code uses the scaled reduction in <exponential-family deviance>,
$$
T=\frac{21.061-18.185}{0.31},
$$
and compares it with $\chi_3^2$.
That chi-squared calibration is appropriate when the dispersion is known, and is asymptotically valid after consistent dispersion estimation. With unknown Gamma dispersion, the standard finite-sample GLM comparison instead uses
$$
F=\frac{(21.061-18.185)/3}{0.3103711}
$$
against an $F_{3,57}$ distribution. Its p-value is approximately $0.034$, so the correctly calibrated test still rejects at the 5% level and gives evidence that component type or position contributes to mean failure time.
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