Gemology Certification Data Analysis & Decision Making 2

Question 1

A gemologist records the following refractive index readings for five stones: 1.544, 1.548, 1.543, 1.546, 1.544. What is the mean RI?

Accepted Answer

1.545

Answer

The mean is (1.544+1.548+1.543+1.546+1.544)/5 = 7.725/5 = 1.545.

Question 2

When plotting specific gravity values on a scatter chart, which axis conventionally represents the measured variable being tested?

Accepted Answer

Y-axis (vertical)

Answer

In scientific data plots the dependent or measured variable is placed on the Y-axis by convention.

Question 3

A buyer receives 20 diamonds graded VS1 by one lab and SI1 by another. What is the BEST first analytical step?

Accepted Answer

Re-examine each stone under 10× loupe to compare inclusions

Answer

Examining inclusions directly allows the gemologist to understand the discrepancy before making any commercial decision.

Question 4

Which statistical measure best describes the spread of fluorescence intensities across a parcel of 100 diamonds?

Accepted Answer

Standard deviation

Answer

Standard deviation quantifies how spread out values are around the mean, making it ideal for describing variability in a dataset.

Question 5

A gemologist plots UV fluorescence intensity versus color grade for 50 diamonds and sees a downward trend. This relationship is best described as:

Accepted Answer

Negative correlation

Answer

A downward trend between two variables indicates a negative correlation.

Gemology Certification Practice Test