麻烦老师解释一下答案:不明白14.38是怎么得来的?

NO.PZ2022081802000053

问题如下：

Three equity fund managers have performance records summarized in the following table:

Given a risk-free rate of return of 2.60%, which manager performed best based on the Sharpe ratio?

选项：

A.Manager 1

B.Manager 2

C.Manager 3

解释：

Solution

C is correct. The Sharpe ratio (^SR) $(\hat{SR})$ is the mean excess portfolio return per unit of risk, where a higher Sharpe ratio indicates better performance:^SR1=ˉRp−ˉRfˆσp=14.38−2.6010.53=1.12 ${\hat{S R}}_{1} = \frac{{\bar{R}}_{p} - {\bar{R}}_{f}}{{\hat{σ}}_{p}} = \frac{14.38 - 2.60}{10.53} = 1.12$ ^SR2=ˉRp−ˉRfˆσp=9.25−2.606.35=1.05 ${\hat{S R}}_{2} = \frac{{\bar{R}}_{p} - {\bar{R}}_{f}}{{\hat{σ}}_{p}} = \frac{9.25 - 2.60}{6.35} = 1.05$ ^SR3=ˉRp−ˉRfˆσp=13.10−2.608.23=1.28 ${\hat{S R}}_{3} = \frac{{\bar{R}}_{p} - {\bar{R}}_{f}}{{\hat{σ}}_{p}} = \frac{13.10 - 2.60}{8.23} = 1.28$