Answer:
Decision rule: Do not reject
; we cannot conclude that the mean differs from zero
Explanation:
From the given information:
The null hypothesis and alternative hypothesis is given as:

And the 99% confidence interval for the population mean
is: [−3.79, 5.86]
The significance level ∝ = 1 - 0.99 = 0.01
We will notice that the 99% confidence interval for the population mean
contains the null hypothesis mean value which is equal to zero.
Thus, we do not reject the null hypothesis at the significance level ∝ = 0.01
∴
Decision rule: Do not reject
; we cannot conclude that the mean differs from zero