Question

1. pH measurements of a chemical solutions have mean 7.5 with standard deviation 0.06. Assuming all pH measurements of this solution have a nearly symmetric/bell-curve distribution. Find the percent (%) of pH measurements reading below 7.5 OR above 7.62.

My answer- 52.28% - wrong

2. Salaries for senior Civil engineers per year have known mean of 70 K dollars and standard deviation 3 K dollars. Provided that the salaries per year for senior Civil engineers have a nearly symmetric/bell-curve distribution, what percent (%) of Civil engineers have salary between 64 K and 67 K dollars?

My answer- 13.59% - wrong

3. Thickness measurements of ancient prehistoric Native American pot shards discovered in a Hopi village are approximately normally distributed, with a mean of 4.2 millimeters (mm) and a standard deviation of 0.6 mm. What percent (%) of ancient prehistoric Native American pot shards discovered in this area has thickness measurement thicker than 5.4.

My answer- 2.28% - wrong

4. Final exam scores in a Math class with large number of students have mean 150 and standard deviation 7.5. Provided the scores of this Final exam have a nearly symmetric/bell-curve distribution, what percent of students score below 127.5 OR above 157.5

My answer- 16% - wrong

Answer 1