EXAM 1 Mastercards pt. 2

Question 1

What is the purpose of sampling in chemical analysis?
A. To eliminate errors in analysis
B. To collect a representative sample for analysis
C. To increase the amount of material for analysis
D. To ensure the sample is homogeneous

Answer 1

B. To collect a representative sample for analysis

Sampling is the process of collecting a representative sample, which is crucial for ensuring the analysis accurately reflects the population.

Question 2

What is the difference between a lot and a batch?
A. A lot is smaller than a batch
B. A batch is derived from multiple lots
C. A lot is a portion of a consignment, while a batch is produced in a single manufacturing cycle
D. A batch contains samples from different consignments

Answer 2

C. A lot is a portion of a consignment, while a batch is produced in a single manufacturing cycle

A lot refers to a portion of a consignment, while a batch is a smaller, defined quantity produced in one manufacturing cycle, often under the same conditions.

Question 3

Which of the following best describes a homogeneous sample?
A. A sample where the properties vary throughout
B. A sample taken from a single layer of material
C. A sample with consistent properties throughout
D. A mixed sample with different layers or phases

Answer 3

C. A sample with consistent properties throughout

A homogeneous sample has consistent properties throughout, making it easier to obtain a representative sample.

Question 4

In which scenario would a static sample be taken?
A. Sampling water from a flowing river
B. Sampling air from a moving vehicle
C. Sampling a liquid from a sealed container
D. Sampling soil from different layers in the ground

Answer 4

C. Sampling a liquid from a sealed container

Static sampling refers to taking a sample from a contained or stationary source where the conditions do not change, such as a sealed container.

Question 5

Which type of sampling ensures each member of the population has a known, non-zero chance of being selected?
A. Convenience sampling
B. Systematic random sampling
C. Snowball sampling
D. Selective sampling

Answer 5

B. Systematic random sampling

In systematic random sampling, each member has a known, non-zero chance of being selected, ensuring a more representative sample.

Question 6

Which sampling method divides the population into subgroups and randomly selects samples from each subgroup?
A. Simple random sampling
B. Stratified random sampling
C. Cluster sampling
D. Consecutive sampling

Answer 6

B. Stratified random sampling

Stratified random sampling divides the population into subgroups (strata), ensuring that all subgroups are represented in the sample.

Question 7

Which of the following is a non-probability sampling method?
A. Simple random sampling
B. Systematic random sampling
C. Selective (Judgmental) sampling
D. Stratified random sampling

Answer 7

C. Selective (Judgmental) sampling

Selective or judgmental sampling is based on the researcher’s judgment and is not random, making it a non-probability method.

Question 8

What is the primary disadvantage of non-probability sampling methods?
A. They are too expensive
B. They introduce bias and limit generalizability
C. They are too time-consuming
D. They require a large population

Answer 8

B. They introduce bias and limit generalizability

Non-probability sampling can introduce bias because not all members of the population have a chance of being selected, which limits the ability to generalize the results.

Question 9

What is snowball sampling typically used for?
A. Large, homogeneous populations
B. Easily accessible populations
C. Hard-to-reach or hidden populations
D. Populations with multiple layers

Answer 9

C. Hard-to-reach or hidden populations

Snowball sampling is often used for hard-to-reach populations, where participants help recruit others by referring them.

Question 10

Which of the following best describes quota sampling?
A. Samples are selected without considering the population’s subgroups
B. Samples are randomly selected from each subgroup
C. Samples are chosen to meet pre-determined group quotas, but without random selection
D. Samples are taken consecutively over a period

Answer 10

C. Samples are chosen to meet pre-determined group quotas, but without random selection

Quota sampling involves dividing the population into groups and selecting samples to meet pre-determined quotas, but the selection process is not random.

Question 11

In the equation for overall variance s₀² = s²ₐ + s²_sub b, what does s²ₐ represent?
A. Variance due to the sampling operation
B. Variance due to the analytical procedure
C. Total variance of the population
D. Standard deviation of the sample

Answer 11

B. Variance due to the analytical procedure

s²ₐ represents the variance due to the analytical procedure, while s²_sub b represents the variance due to the sampling operation

Question 12

What is the expected number of KCl particles if a mixture contains 1% KCl and 99% KNO₃ particles, and 10,000 particles are sampled?
A. 100
B. 10
C. 1,000
D. 99

Answer 12

A. 100

1% of 10,000 particles is 100, so the expected number of KCl particles is 100.

Question 13

If the expected number of KCl particles in a sample is 100, which statistical distribution is used to calculate the standard deviation of the number of KCl particles in repeated experiments?
A. Normal distribution
B. Poisson distribution
C. Binomial distribution
D. Uniform distribution

Answer 13

C. Binomial distribution

The binomial distribution is used to calculate the standard deviation when drawing particles randomly from a mixture.

Question 14

What is the sampling constant Kₛ used for in sampling?
A. To calculate the total mass of the sample
B. To estimate the number of samples needed
C. To express the mass of a sample that produces a relative sampling standard deviation of 1%
D. To eliminate random errors in sampling

Answer 14

C. To express the mass of a sample that produces a relative sampling standard deviation of 1%

Kₛ is the sampling constant, which represents the mass of a sample that produces a relative sampling standard deviation of 1%.

Question 15

What does the term “representativeness” refer to in sampling?
A. The ability of a sample to produce accurate measurements
B. The degree to which a sample reflects the essential characteristics of the population
C. The homogeneity of a sample
D. The number of particles in a sample

Answer 15

B. The degree to which a sample reflects the essential characteristics of the population

Representativeness refers to how accurately a sample reflects the characteristics of the entire population.

Question 16

Which sampling method involves taking samples at regular intervals after selecting a random starting point?
A. Stratified random sampling
B. Systematic random sampling
C. Cluster sampling
D. Consecutive sampling

Answer 16

B. Systematic random sampling

In systematic random sampling, samples are taken at regular intervals after a random starting point is selected.

Question 17

How does stratified random sampling ensure that all subgroups in a population are represented?
A. By randomly selecting samples from the entire population
B. By dividing the population into clusters and selecting entire clusters
C. By dividing the population into strata and taking random samples from each stratum
D. By taking samples at regular intervals

Answer 17

C. By dividing the population into strata and taking random samples from each stratum

Stratified random sampling divides the population into subgroups (strata) and then takes random samples from each subgroup to ensure representation.

Question 18

What is the variance in sampling caused by?
A. Only the analytical procedure
B. Only the sampling operation
C. Both the analytical procedure and the sampling operation
D. The size of the sample only

Answer 18

C. Both the analytical procedure and the sampling operation

The total variance in sampling is caused by both the analytical procedure and the sampling operation, as reflected in the equation s₀² = s²ₐ + s²_sub b

Question 19

Which sampling method involves selecting entire groups or clusters at random, rather than individual members?
A. Simple random sampling
B. Cluster sampling
C. Stratified random sampling
D. Quota sampling

Answer 19

B. Cluster sampling

In cluster sampling, entire groups (clusters) are randomly selected, rather than individual members from the population.

Question 20

What is the purpose of sample preparation in chemical analysis?
A. To collect more material for analysis
B. To eliminate interfering species and concentrate the analyte
C. To increase the number of samples
D. To reduce the number of analyses needed

Answer 20

B. To eliminate interfering species and concentrate the analyte

Sample preparation involves converting a bulk sample into a homogeneous laboratory sample and eliminating interfering species or concentrating the analyte.