CSCI N207: Data Analysis Using Spreadsheets Copyright ©2005  Department of Computer & Information Science Measurement in Physical and Behavioral Sciences

CSCI N207: Data Analysis Using Spreadsheets Copyright ©2004  Department of Computer & Information Science Goals By the end of this unit, you should understand …By the end of this unit, you should understand … The differences between qualitative and quantitative measurement.The differences between qualitative and quantitative measurement. How researchers in the physical sciences measure phenomena.How researchers in the physical sciences measure phenomena. The differences between direct and indirect measurement.The differences between direct and indirect measurement. The nature of measuring errors.The nature of measuring errors.

CSCI N207: Data Analysis Using Spreadsheets Copyright ©2004  Department of Computer & Information Science The Nature of Measurement Measurement is a process of assigning numerals to observations according to some established set of rules.Measurement is a process of assigning numerals to observations according to some established set of rules. Numbers in measurement eliminate ambiguity in classification and promote uniformity in practice.Numbers in measurement eliminate ambiguity in classification and promote uniformity in practice. Measurements can be qualitative or quantitative depending the how the number system is applied.Measurements can be qualitative or quantitative depending the how the number system is applied.

CSCI N207: Data Analysis Using Spreadsheets Copyright ©2004  Department of Computer & Information Science Quantitative Measurement "Something you can count.""Something you can count." Quantitative analysis is more objective than qualitative analysis.Quantitative analysis is more objective than qualitative analysis. Quantitative analysis is usually easier to display than qualitative analysis.Quantitative analysis is usually easier to display than qualitative analysis.

CSCI N207: Data Analysis Using Spreadsheets Copyright ©2004  Department of Computer & Information Science Qualitative Measurement Qualitative analysis is usually more subjective than quantitative analysis.Qualitative analysis is usually more subjective than quantitative analysis. Considered more “open-ended”Considered more “open-ended” More difficult to display findings …More difficult to display findings …

CSCI N207: Data Analysis Using Spreadsheets Copyright ©2004  Department of Computer & Information Science Measurement in the Physical Sciences Measurements in the physical sciences tend to be quantitative.Measurements in the physical sciences tend to be quantitative. The role of measurement is to enable us to classify attributes or properties of “objects” so that we can fruitfully apply mathematical concepts, theories and techniques in reasoning about them.The role of measurement is to enable us to classify attributes or properties of “objects” so that we can fruitfully apply mathematical concepts, theories and techniques in reasoning about them. In other words, the answer to why we do measurements in the physical sciences is that if we do it properly we will be able to establish mathematical models with equations and prediction capabilities which are the goal of the inquiry.In other words, the answer to why we do measurements in the physical sciences is that if we do it properly we will be able to establish mathematical models with equations and prediction capabilities which are the goal of the inquiry.

CSCI N207: Data Analysis Using Spreadsheets Copyright ©2004  Department of Computer & Information Science Direct Measurements Example: Measuring the length and width of a table.Example: Measuring the length and width of a table. Principle of direct comparison – use an established “standard” to measure a given property of an object (the standard in the previous example could be inches or centimeters).Principle of direct comparison – use an established “standard” to measure a given property of an object (the standard in the previous example could be inches or centimeters).

CSCI N207: Data Analysis Using Spreadsheets Copyright ©2004  Department of Computer & Information Science Indirect Measurement Measurements on a scale outside of human capacity.Measurements on a scale outside of human capacity. Examples:Examples: –The distance from earth to the sun –The size of an atom

CSCI N207: Data Analysis Using Spreadsheets Copyright ©2004  Department of Computer & Information Science Measurement Concepts 1.Resolution – refers to the smallest measurable amount. 2.Accuracy – refers to the fractional error in making a measurement; difference between the measured value and the “actual” value.

CSCI N207: Data Analysis Using Spreadsheets Copyright ©2004  Department of Computer & Information Science Results of the Measuring Process A measurement can be looked upon as a relationship between some property/attribute of a physical system and of quantities that define it (i.e. - the length and width of a desk).A measurement can be looked upon as a relationship between some property/attribute of a physical system and of quantities that define it (i.e. - the length and width of a desk). The measured quantity can always be expressed in different numerical scales and related to each other in precise mathematical ways.The measured quantity can always be expressed in different numerical scales and related to each other in precise mathematical ways.

CSCI N207: Data Analysis Using Spreadsheets Copyright ©2004  Department of Computer & Information Science Errors of Observation Given a well-described experimental procedure to measure certain properties of a “system”, there will be scatter in the results obtained through repeated application of the procedure.Given a well-described experimental procedure to measure certain properties of a “system”, there will be scatter in the results obtained through repeated application of the procedure. This is experimental error – different measured values of the same property using identical measurement process.This is experimental error – different measured values of the same property using identical measurement process.

CSCI N207: Data Analysis Using Spreadsheets Copyright ©2004  Department of Computer & Information Science Errors of Observation (cont.) Error occurs even when the rules of the measurement process is strictly observed.Error occurs even when the rules of the measurement process is strictly observed. They are due to inherent looseness in the these rules:They are due to inherent looseness in the these rules:  Random, accidental, not controllable (incompleteness )  Systematic, repeatable, instrument caused, (inaccuracy)

CSCI N207: Data Analysis Using Spreadsheets Copyright ©2004  Department of Computer & Information Science Questions?

References Jeff Allen. N207 Lecture Notes.Jeff Allen. N207 Lecture Notes.