Standard Normal Curve
Table practice:
Use Table A to find the proportion of observations from a standard normal
distribution that satisfies each of the following statements. In each case, sketch a
standard normal curve and shade the area under the curve that is the answer to the
question.
1) z < 2.45
2) z > 2.68
3) z > -1.65
4) z < -0.56
5) z > 3.70
6) -1.22 < z < 0.75
7) z < -1.65
8) Find the z-score with 30% of the data falling above it
9) Find the z-score with 20% of the data falling below it
2.23 Page 103
The distribution of heights of adult American men is approximately normal with
mean 69 inches and a standard deviation of 2.5 inches.
What percent of the men are under 6 feet tall?
a) standardize this value to determine how many standard deviations from the
mean 72 inches is. Sketch the graph.
z=
b) Find the z score on the table and read the proportion.
c) Answer the question.
What percent of the men are between 5 feet 5 inches and 6 feet tall?
a) standardize both values and sketch
z=
z=
b) find the two values on the table
c) find the proportions for each value.
d) subtract the smaller proportion from the larger one.
What percent of the men are at least 5’10”
a) standardize this value and sketch
b) find the z-score on the table
c) find the proportion of men are less than 5’10’’ tall.
d) subtract this proportion from 1.00.
e) answer the question.
How tall must an adult American be to be in the tallest 10%?
a) find .10 on the interior of the the table
b) Read up and left to determine the z-score
c) plug the z-score into the formula and solve for x
1.28 = ____________________