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Lecture 3

2012.09.27 PSYB01H3 week 3 .docx

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Connie Boudens

Week 3 PSyb01h3 2012-09-27 Basic Issues and Concepts -------------------Variables: their types and purpose in research Measurement issues Variables  Definition: something that varies! Something that could take on different values. o Feature of a person, situation, etc, that can take on one value or more.  Examples: level of creativity, numbers of siblings, height, room temperature, color of food. o Main purpose of research is to simplify the complex by explaining variability.  Variability in behaviour o Differences in the way people behave in response to the same stimulus o Types:  systematic (explained): explainable variability  random (unexplained) o Ex: a mouse runs through the classroom..  What could I do? I may be shocked. But other ppl may react differently, like creaming, or some ppl may be calm.  Psychology is trying to know why ppl behaving in certain way. Particular stimulus affect ppl in different way.  What matters here?  Gender? Women is more sensitive, men are likely to take charge the situation  City Vs. country person? Urban ppl more scared; country ppl is more calmed?  Animal lovers? Maybe someone is more tolerated  Color of mouse? Black mouse is more scary?  Still some variation in responses left between ppl ----this is random----for now…  Other points: o Variables must have 2+ values or levels o Value: number representing one of many possible “states” of the variable  Example: some possible values of height are 6’, or 4’2” o Score: a specific value for a given person  Example: my score on the variable of height is 5’7”  Independent vs. dependent variables o Independent variable: I.V  manipulated by researcher –  assumed to be cause o Dependent variable:  outcome of experiment  measurable and it is measured  Assumed to be caused by i.v. o the D.V. Depends on the IV. And I.V causes the D.V.  What’s the i.v? What’s the d.v? o There will be a difference between the number of boys and the number of girls pushing and shoving in the playground  I.V.: gender  D.V. pushing and shoving o There will be a difference between the number of words recalled by participants who have learned them in a noisy room and participants who have learned the same words in a quiet room  I.V.: level of noise in the room;  Two values: quiet and noisy  D.V: number of words recalled depend on the noise level in the room o People who suffer with a serious mental disorder are more likely to take more medication than people who do not suffer with a serious mental disorder.  IV. Mental disorder  Two values; serious mental disorder VS. anybody else  DV. medication taken o Students who sit further forward in class will achieve a higher grade in the final examination  I.V: where you sit in class; level is not identified  D.V. grade in the course  Measuring Variables o First-step: determining whether variable is categorical or continuous.  Categorical (taxonic, qualitative, nominal):  Values are discrete, qualitatively different categories  Measured on nominal scale o Biological sex is always considered as nominal variables  Nominal means in name only.  Some categorical variables are nominal variables o Like gender, political parties  Continuous: you could have different values on a certain variables  Values differ in degree from each other  Measured on ordinal, ratio, or interval scale  Determines how you can analyze data  Example: you want to figure out the relationship between age and phone book use to serve for a yellow page printing company o You ask ppl in different ways to see if they have phone books o You got two categories: age under or above 25 yrs old; two groups of ppl  Scales of measurement o Scales of Measurement: Ordinal  Ordered or ranked data  Intervals may or may not be equal  Ex: finishing place in race  It does not mean the difference the different place are equal  It is just a ranking data  They reason you have to figure what kind of data is measured is for the statistical purpose. Actually, the ranking data is hard to be statistic . o Scales of Measurement: Interval  Ordering, but with equal intervals  Ex: temperature  The "zero point" is arbitrary, and values can be negative  Everything is relative; zero is meaningful o Scales of Measurement: Ratio  Same as interval, but with a true zero point (i.e. 0 quite literally means none)  Ex:  Money in your wallet  Time to finish race  Scales of Measurement Summary  Measuring Variables o Operational definition: clearly Procedures for measuring or manipulating the variable  It is related to how you will measure the variables o Specific enough to allow replication—that someone would be able to do your study without contact you.  Straightforward for concrete variables, more challenging for abstract ones.  You have to make decision how you will measure your variablesa key decision  Operational definitions – let’s try some... o Examples: - You may have different ways to measure the stress of a person; like # of negative life events - The way you choose to study will affect you research - For example, you want to do the physiological patterns Vs stress o You may need to face the person, and you may need many machines to measure o Which may make you research very expensive o Then your research may not be replicable - There is no perfect way but may be better way of worse way in doing pa
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