Researchers reported the means for each condition. Which of the following would be more useful in understanding that these means are just estimates of the underlying population mean?

(M = 12.89, SD = 3.98), t (27) = - 0.14, p = 0.88

(M = 14,97, SD = 5.05), t (30) = 2.17, p = 0.03

a. Confidence intervals around each mean would give us a sense of the range of plausible values for these means.

b. An analysis of statistical power would be us understand how likely it us for this study to lead to these particular means.

c. An effect size, such as Cohen's d, would help us to understand more about the means.

d. Knowing the standard errors, in addition to the standard deviations, would give us a better understanding of these means.