statistics assignment 12

I need some help understanding my statistics hw. Here are the assignments:

 

t-Tests

 

In looking at your business, when and why would you want to use a one-sample mean test (either z or t) or a two-sample t-test?  Create a null and alternate hypothesis for one of these issues.  How would you use the results?  

 

Variation

 

Variation exists in virtually all parts of our lives. We often see variation in results in what we spend (utility costs each month, food costs, business supplies, etc.).  Consider the measures and data you use (in either your personal or job activities). When are differences (between one time period and another, between different production lines, etc.) between average or actual results important?  How can you or your department decide whether or not the variation is important?  How could using a mean difference test help?

 

Thank you!