1-Identify each study as observational or experimental.

a. A researcher stood at a busy intersection to see if the color of an automobile is related to running red lights.

b. Subjects were randomly assigned to two groups. One group was given an herb, the other group was given a placebo.

2- Shown here are two frequency distributions. Each is incorrectly constructed. Explain why. Read on Frequency Distribution in textbook to answer this.

3- The grades on a recent quiz are shown below. Construct a stem-and-leaf plot for the data.

a. Class 27-32 33-38 39-44 45-49 50-55 Frequency 1 0 6 4 42 2 b. Class Frequency 27-32 1 39-44 6 45-50 4 51-56 57-62 2 7 29 83 92 67 83 96 92 67 75 67 79 92 83 58 75 79 67 92 75 92