Part of a usability study to assess voting machines measured the time on task (TOT) of voters casting ballots (efficiency). Specifically, the data are for the same ballot cast on two different voting machines at the same location (called a precinct). Your job is to perform a "t" test on these data and draw conclusions about which voting machine is better in terms of usability. A few background items:
• The voters (participants/users) are a homogeneous group.
• Voters were randomly assigned to the voting machines.
• Thus, the two groups of voters (one group using the DRE voting machine, and the other using the OptiScan voting machine) have equal variances.
• We have no advance information to indicate that one voting machine will be better than the other. If you need a refresher of the "t" test, read the "t-test description. pdf"
Question1 – What is the null hypothesis in this usability study?
Question 2 – How many degrees of freedom are in each group (the DRE and OptiScan groups)?
Question 3 – Which "t" test should be used – paired, unpaired/equal variance, unpaired/unequal variance?
Question 4 – Should a one-tail, or two-tailed test be used, and why?
Question 5 – What is the t value?
Question 6 – Is the t value significant at the 0.05 level, and why?
Question 7 – Is the t value significant at the 0.01 level, and why?
Question 8 – Considering the combination of the above analysis, and the number of ballots completed, which voting machine has better usability, and why?