Znajdowanie krytycznej wartości t* dla określonego poziomu ufności

Emilio took a random sample of $n=12$n, equals, 12 giant Pacific octopi and tracked them to calculate their mean lifespan. Their lifespans were roughly symmetric with a mean of $\bar x=4$x, with, \bar, on top, equals, 4 years and a standard deviation of $s_x=0.5$s, start subscript, x, end subscript, equals, 0, point, 5 years. He wants to use this data to construct a $t$t interval for the mean lifespan of this type of octopus with $90\%$90, percent confidence.