# Scores on a test are normally distributed with a mean of 68.2 and a standard deviation of 10.4. What is the probability that among 75 randomly selected students, at least 20 of them score greater than 78?

##### 1 Answer

#### Explanation:

Let say,

therefore,

To find a probability that at least more than 20 of 75 students score greater than 78 marks,

where

We also can calculate as