Yuan and Maxwell (2005) investigated how the power of a study influences the decisions researchers make in an experiment. In their introduction concerning effect size, they stated that "the exact true effect size is generally unknown even after the experiment. But one can estimate the effect size ... [and] when the sample size is large the estimated effect size is near the true effect size" (Yuan & Maxwell, 2005, p. 141).

(a) Why is the "exact true effect size" generally unknown even after the experiment? Explain.

(b) How does increasing the sample size improve our estimate of effect size when we use estimated Cohen's d?