For each number, determine the type of inference, state the assumptions, and answer the questions.

1. A random survey of 57 students was conducted to compare juniors and seniors employment status. Seven out of 18 juniors held a job while 16 out of 39 seniors held a job. (a) Find and interpret a 98% confidence interval. (b) Is there evidence at the 1% significance level that more seniors have a job than juniors? If so, what might explain this?

2. Cocaine addicts need cocaine to feel any pleasure, so perhaps giving them an antidepressant drug will help. A three-year study with 72 chronic cocaine users compared an antidepressant drug called desipramine against lithium (a standard drug to treat cocaine addiction), and of course a placebo as well. The subjects were randomly assigned to receive each treatment. Here are the results:

| | Cocaine Relapse? | Group | Treatment | Yes | No | 1 | Desipramine | 10 | 14 | 2 | Lithium | 18 | 6 | 3 | Placebo | 20 | 4 |

(a) Make a graph to compare the rates of cocaine relapse for the three treatments. Describe what you see. (b) Is there a relationship between Treatment and Cocaine Relapse?

3. A random study of 25 people on whether fidgeting and other “non-exercise activity” (NEA) can explain why some people don’t gain weight when they overeat was done. Output for this study is shown below.

Regression Analysis: Fat gain versus NEA change | Predictor | Coef | SE Coef | T | P | Constant | 3.5051 | 0.3036 | 11.54 | 0.0003 | NEA change | -0.065 | 0.014 | | | s = 0.75 | R-Sq = 92.5% | R-Sq(adj) = 95.6% |

(a) Explain what s = 0.75 means. (b) Find and interpret a 90% confidence interval for the slope of the regression line. (c) Does a linear relationship exist between fidgeting and NEA change?

4. A statistics student wants to compare the mean times needed to access flight information for two major