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Lecture 3

FDSN 507 Midterm 1

Define accuracy. How close a particular measure is to the true or correct value.
Define precision. How reproducible or how close replicate measurements are.
To determine accuracy, compare the ______ to the true value. mean
Accuracy is assessed by _____ error or _____ error. absolute, relative
Define absolute error. The difference between experimental value and true value.
Define relative error. Compares the difference between experimental value and true value against the true value.
T or F: Absolute error is more useful than relative error. False
How can precision be assessed? Standard deviation, coefficient of variation, confidence interval, standard error
Define standard deviation. How close a set of values are to each other.
Define coefficient of variation. Relative standard deviation.
A confidence interval uses ____ values for more than 25 samples and ____ values for less than 25 samples. Z, t
Define systematic error. Results which consistently deviate from true value.
Define random error. Results which fluctuate; unavoidable.
Define blunders. Results which are completely off; "screw up".
Define sensitivity. The magnitude of change in measurement with change in concentration of a compound.
Define limit of detection. The lowest possible increment that statistical significance can be detected.
What two values are similar to limit of detection? Method detection limit, limit of quantitation
What are standard curves used for? To determine unknown concentrations.
______ regression is most often used to construct a curve. Linear
Define correlation coefficient. How well data fit to a straight line.
Define coefficient of determination. How much of a measurement is explained by regression.
What is the Q test used for? To determine if outliers are present in data and whether or not they should be accepted or rejected.
What three things should a sampling plan be? Simple and flexible, protect consumers and vendors, ensure reliable results.
To ensure that the estimated value obtained from the ______ _______ is a good representation of the true value of the ______ it is necessary to develop a ______ ______. laboratory sample, population, sampling plan
What details should be included in a sampling plan? Sample size, locations, method, preservation
Define official samples. Samples selected for official or legal requirements by government.
Why might raw materials be analyzed? To ensure they are good quality.
Techniques for monitoring _____ _____ samples must be capable of producing precise results in a short time. process control
Define attribute property. Something a product either does or does not have.
Define variable property. Something that can be measured on a continuous scale.
T or F: Variable sampling requires less samples than attribute sampling. True
Give an example of a finite population. A truckload of apples.
Give an example of an infinite population. A conveyor belt which operates continuously.
Define a continuous population. A population which has no separation between different parts of the sample.
Define a compartmentalized population. A population which is split up into subunits.
Define heterogeneous population. The properties of an individual sample vary with location.
Define acceptance sampling. Determine if a shipment of products or ingredients has the quality to be accepted.
Define skip-lot sampling. Only a fraction of the submitted lots is inspected; only can do with a trusted supplier.
What is the consumer's risk associated with samapling? Probability of accepting poor quality population <5% of the lots.
What is the producer's risk associated with sampling? Probability of rejecting good quality population 5-10% of the lots.
Describe how flour sampling is conducted. Square root of number of sacks in the lot; draw sample from corner diagonal to center; draw sample from opposite corner; store sample in dry place
Give examples of manual sampling. Sample from different locations, mix properly
T or F: Continuous sampling is more prone to human bias. False
In _____ sampling, an investigator selects a sample deliberately. nonprobability
How should a sample size be determined? Precision or power analysis
Precision analysis is based on a _____ _____. confidence interval
Name three problems in sampling procedures. Sampling bias, sample degradation due to storage, mistaken sample identification
Name two methods of sample grinding. Rototap, mesh number
What is a rototap? An instrument which separates small particles based on size.
Define mesh number. Number of square openings per linear inch.
A mesh number of ___ should be used for moisture, protein, or mineral analysis. 20
Name three considerations for sample preparation. Enzyme activity, lipid oxidation, microbial growth, physical changes
Created by: goberoi



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