Two sigma

Khail took his math test and scored 88. If the class average was 78 with a standard deviation of 5, what percent of students earned a higher grade than Khail's grade?

Correct answer:

p =  2.275 %

Step-by-step explanation:

$$\begin{gathered} K=88 \\ m=78 \\ \sigma =5 \\ K=m+2\cdot \sigma =78+2\cdot 5=88 \\ p=(100-95.45)/2=2.275\% \end{gathered}$$

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