A manufacturer knows that their items have a normally distributed length, with a mean of 10.2 inches, and standard deviation of 1.8 inches. If 25 items are chosen at random, what is the probability that their mean length is less than 9.8 inche

P [ X ≤  9.8 ]  = 0.1335

Step-by-step explanation:

P [ X ≤  9.8 ]  =  [ ( 9.8  - 10.2 )/1.8√25 ]

P [ X ≤  9.8 ]  =  - 0.4*5/1.8

P [ X ≤  9.8 ]  = - 2 / 1.8

P [ X ≤  9.8 ]  =  - 1.11

From z- table we get:  α  =  0.1335

P [ X ≤  9.8 ]  = 0.1335   or   P [ X ≤  9.8 ]  = 0.1335

the answer is b