Analytical Chemistry: Basic Statistics and Chemometrics

The concentration of a solution is known to be 0.101 M. A student determines the concentration to be 0.088 M, 0.087 M, and 0.089 M for each titration performed. Which of the following best describes these results?

• The results are both accurate and precise

• The results are neither accurate nor precise.

• The results are precise but not accurate

• The results are accurate but not precise.

Glucose levels are routinely monitored in patients suffering from diabetes. The glucose concentrations in a patient with mildly elevated glucose levels were determined in different months by a spectrophotometric analytical method:

Month 4: 799, 745, 750, 774, 777, 800, 758

What is the mean of the glucose concentration on Month 4?

• 729 mg/L

• 768 mg/L

• 772 mg/L

• None of these

Water Hardness Data (ppm):

259, 271, 271, 274, 278, 281, 286, 289

What is the relative standard deviation?

• 8.95

• 0.0347

• 9.57

• 3.47

Glucose levels are routinely monitored in patients suffering from diabetes. The glucose concentrations in a patient with mildly elevated glucose levels were determined in different months by a spectrophotometric analytical method:

Month 1: 1108, 1122, 1075, 1099, 1115, 1083, 1100

What is the mean of the glucose concentration on Month 1?

• None of these

• 1108 mg/L

• 1155 mg/L

• 1100 mg/L

Water Hardness Data (ppm):

259, 271, 271, 274, 278, 281, 286, 289

What is the mean?

• 276.00 ppm

• 271.13 ppm

• 271.00 ppm

• 276.13 ppm

Sewage and Industrial pollutants dumped into a body of water can reduce the dissolved oxygen concentration and adversely affect aquatic species. In one study, weekly readings are taken from the same location in a river over a 2-month period.

Can the week 3 value be rejected at 95% confidence level? Gtab = 2.032

• No, G = 1.774

• Yes, G = 1.897

• No. G = 1.897

• Yes, G = 1.774

Glucose levels are routinely monitored in patients suffering from diabetes. The glucose concentrations in a patient with mildly elevated glucose levels were determined in different months by a spectrophotometric analytical method:

Month 3: 788, 805, 779, 822, 800

What is the mean of the glucose concentration on Month 3?

• 799 mg/L

• 779 mg/L

• 805 mg/L

• 800 mg/L

Which of the following is not a systematic error?

• Wrong precipitant used in gravimetry

• Incomplete precipitation in gravimetry

• Wrong volume reading in buret

• Out-of-date instrument calibration

Glucose levels are routinely monitored in patients suffering from diabetes. The glucose concentrations in a patient with mildly elevated glucose levels were determined in different months by a spectrophotometric analytical method:

Month 2: 992, 975, 1022, 1001, 991

What is the mode of the glucose concentration on Month 2?

• None of these

• 101 mg/L

• 996 mg/L

• 992 mg/L

Two students are tasked with determining the milligrams of chloride in a simulated soil sample. Both students extract chloride into an aqueous solution and perform triplicate titration with silver nitrate solution and dichlorofluorescein indicator. The students report the following results to their laboratory instructor.

If the accepted value is 36.90 mg chloride/g sample, the laboratory instructor infers that student #1’s work exhibits ___ student #2.

• higher accuracy and lower precision than

• higher accuracy and higher precision than

• lower accuracy and higher precision than

• results impossible to differentiate from

• lower accuracy and lower precision than