Based on data compiled by the World Health Organization, the mean systolic blood pressure in the
United States is 120, the standard deviation is 16, and the pressures are normally distributed. Find
The percent of individuals who have blood pressure between 120 and 128.
A)15.9%
B)19.2%
C)22.7%
D)9.3%

Question

Quizplus · Accepted Answer

To find the percentage of individuals with blood pressure between 120 and 128, we need to find the area under the normal distribution curve between these two values. First, we need to standardize both values using the formula:
z = (x - mu) / sigma
where x is the value (either 120 or 128), mu is the mean (120), sigma is the standard deviation (16), and z is the standardized score.

For x = 120:
z = (120 - 120) / 16 = 0

For x = 128:
z = (128 - 120) / 16 = 0.5

Next, we use a standard normal distribution table or calculator to find the area under the curve between z = 0 and z = 0.5. From a standard normal distribution table, the area between z = 0 and z = 0.5 is 0.1915 or 19.15%.

Therefore, the percentage of individuals with blood pressure between 120 and 128 is approximately 19.2%. Thus, the best choice is B. We need to find the area under the normal curve between 120 and 128. 
Using the z-score formula: 
z = (x - μ) / σ
where 
x = 128 (upper limit)
μ = 120 (mean)
σ = 16 (standard deviation)
z = (128 - 120) / 16 = 0.5
Using a standard normal distribution table, we can find the area to the left of z = 0.5, which is 0.6915. 
Similarly, using z = (120 - 120) / 16 = 0, we can find the area to the left of z = 0, which is 0.5. 
Therefore, the area between z = 0 and z = 0.5 is 0.6915 - 0.5 = 0.1915. 
Converting this to a percentage, we get 19.15%, which is closest to 19.2%. Thus, the answer is B) 19.2%.

Based on Data Compiled by the World Health Organization, the Mean