A researcher wanted to examine whether type of dog food (freeze dried meat vs generic brand kibble) would affect dogs' attention span. The researcher hypothesized that dogs who ate freeze dried meat would have longer attention spans than those who ate generic brand kibble. The researcher used a single sample of 13 subjects, that took part in both treatment conditions. The alpha level was .01.

What is the critical test statistic?

What is the appropriate statistical test to use?

Should the researcher use one-tailed or two tailed?