Answer:
b. We do not have enough information to make a conclusion.
Step-by-step explanation:
For testing difference of means our null hypothesis and alternative hypothesis is
H0: There is no significant difference between the average packing time of old machine and new machine i.e. μold-μnew=0.
Ha:There is significant difference between the average packing time of old machine and new machine i.e. μold-μnew≠0.
When the confidence contains the null values then there is no significant difference exists. Here the specified null value is 0. A 95% confidence interval (-6.85, 0.34) shows that it contains null value so, there is no significant difference between the average packing time of the two machines at 5% level of significance. This results is for 95% confidence interval. For 90% confidence interval result may vary and we don't have sufficient information given to compute 90% confidence interval.