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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 |

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goberoi