Roger D. answered • 11/22/20
Math Tutor Specialized in Statistics, Algebra, and Trigonometry
Given that X has a normal distribution with mean 10 and standard deviation 2,find:
- P(9 <=X <=12)
Step 1: Find the Z scores for 9 and 12.
z1 = (9-10)/2 = -1/2
z2 = (12-10)/2 = 1
Step 2: Use table or TI-84 to find area under the curve.
TI-85 normalcdf ( -1/2, 1) = .5328
Table: Area (1) - Area (-1/2) using standard z tables
Area = .8413 - ..3085 = .5328
2 If P(a <= X <= b) = 0.95, then find a and b.
Step 1: Find the z-scores for Areas of 0.025 and 0.975
z1 = -1.96 and z2 = 1.96
Step 2: Find the x-score for each
x1 = (-1.96)(2) + 10 = 6.08
x2 = (1.96)(2) + 10 = 13.92
Liam R.
Hi Sir, can you pls explain this without excel?11/22/20