Probability that 3 of 7 items weigh between 8 and 16 ounces

[619snake]

need help with this problem
x~normal(mean= 12, stdev=2)
item weight from 8 to 16 ounces
i have a random sample of 7 items and need to find the probability that 3 of those items fulfill the weight
each item is independent

this is what i got at the moment
z=(16-12)/(2) = 2
p(z<2)-p(z<-2)
=.9772-.0228
=.9544

 

[rock.freak667]

You need to use the transformation Z=(X-μ)/σ, and then read the range off of your table.

(σ = std.dev, and μ=mean)