Biology Forums - Study Force

Before you took this course, you probably heard many stories about Statistics courses. Oftentimes parents of students have had bad experiences with Statistics courses and pass on their anxieties to their children. To test whether actually taking AP* Statistics decreases students' anxieties about statistics, an AP* statistics instructor gave a test to rate student anxiety at the beginning and end of his course. Anxiety levels were measured on a scale of 0-10. Here are the data for 16 randomly chosen students from a class of 180 students:




Create and interpret a 90% confidence interval.

Under these conditions the sampling distribution of the differences can be modeled by a Student's t-model with (n - 1) = 15 degrees of freedom, and we will use a paired t-interval.
The 90% critical value for t₁₅ is 1.753 (from table).
The margin of error:  ME = t*₁₅ × SE() = 1.753(0.287) = 0.503
So the 90% confidence interval is -1.125 ± 0.503, or an interval of (-1.63, -0.62).
We are 90% confident that taking AP* Statistics will decrease a student's anxiety between 0.6 and 1.6 points (on our scale).