Summary statistics for the two groups from Minitab are provided.

a. Explain why it is acceptable to use two-sample t procedures in this setting.

b. Construct and interpret a 95% confidence interval for the difference in the mean English grade for light and heavy readers.

c. Does the interval in part (b) provide convincing evidence that reading more causes a difference in students’ English grades? Justify your answer.

Do students who read more books for pleasure tend to earn higher grades in English? The boxplots show data from a simple random sample of 79 students at a large high school. Students were classified as light readers if they read fewer than 3 books for pleasure per year. Otherwise, they were classified as heavy readers. Each student’s average English grade for the previous two marking periods was converted to a GPA scale, where A = 4.0, A− = 3.7, B+ = 3.3 and so on.

of reader Mean StDev SE Mean Heavy 47 3.640 0.324 0.047 Light 32 3.356 0.380 0.067