In 31 games of the regular season of Major League Baseball, an average of 77.9 home runs per game were achieved

Task:

In 31 games of the regular season of Major League Baseball, an average of 77.9 home runs per game were achieved with an empirical standard deviation of 8.89. Assume that the number of home runs is normally distributed.

Enter the upper limit of the 90% confidence interval for the expected number of home runs per game.

Problem / approach:

I have calculated the task as in the other explanations, but I get 75.85, but it’s wrong … please help: D