A Sports Analyst Claims That the Mean Batting Average for Teams

question 112

Essay

A sports analyst claims that the mean batting average for teams in the American League is not equal to the
mean batting average for teams in the National League because a pitcher does not bat in the American League.
The data listed below are random, independent, and come from populations that are normally distributed. At $\alpha$ α = 0.05, test the sports analystʹs claim. Assume the population variances are equal. $\text { American League }$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\text { National League }$
$\begin{array}{c}\begin{array}{llll}0.279 & 0.274 & 0.271 & 0.268 \\0.265 & 0.254 & 0.240 &\end{array}\begin{array}{llll}0.284 & 0.267 & 0.266 & 0.263 \\0.261 & 0.259 & 0.256 &\end{array}\end{array}$

Understand the threats to internal validity in one-group pretest-posttest designs and other quasi-experimental designs.

Recognize the importance of control features in quasi-experimental designs to approximate true experimental conditions.

Understand the effect of interventions and the importance of measuring their reversibility.

Understand the concept of marginal utility and its impact on total utility.

---

Definitions:

Pelvic Cavity

A body cavity that is bounded by the bones of the pelvis, containing reproductive organs, the urinary bladder, and the rectum.

Body Cavities

Defined spaces within the body that house organs and other structures, such as the thoracic, abdominal, and pelvic cavities.

Mesentery

A double layer of peritoneum that attaches the intestines to the wall of the abdomen, providing support and containing blood vessels, nerves, and lymphatics.

Serous Membrane

A thin membrane that lines certain internal cavities, producing serous fluid to reduce friction between internal organs.