EXAM 1 Mastercards pt. 2 Flashcards
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
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.
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
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.
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
C. A sample with consistent properties throughout
A homogeneous sample has consistent properties throughout, making it easier to obtain a representative sample.
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
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.
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
B. Systematic random sampling
In systematic random sampling, each member has a known, non-zero chance of being selected, ensuring a more representative sample.
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
B. Stratified random sampling
Stratified random sampling divides the population into subgroups (strata), ensuring that all subgroups are represented in the sample.
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
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.
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
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.
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
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.
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
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.
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
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
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
A. 100
1% of 10,000 particles is 100, so the expected number of KCl particles is 100.
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
C. Binomial distribution
The binomial distribution is used to calculate the standard deviation when drawing particles randomly from a mixture.
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
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%.
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
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.
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
B. Systematic random sampling
In systematic random sampling, samples are taken at regular intervals after a random starting point is selected.
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
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.
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
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
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
B. Cluster sampling
In cluster sampling, entire groups (clusters) are randomly selected, rather than individual members from the population.
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
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.
