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PSYC 258: Chapter 1
Terminology & Scales of Measurement
Preview
Terminology
Scales of Measurement
Notation & Math Basics
Learning Objectives
By the end of this class you should be able to…
1. Apply terminology relevant to the field of Statistics
2. Compare the different scales of measurement and give examples of each
3. Explain why scales of measurement matter
4. Properly use symbols and basic math rules
Terminology
What is Statistics?
What are the two branches?
What types of questions can Statistics answer?
Terminology
What is a Hypothesis?
Hypothesis “an educated guess”
Hypothesis a testable prediction (based on prior evidence)
Terminology
Null Hypothesis everything that does not support what the researcher wants to find; what is already assumed
Research Hypothesis what the researcher wants to find evidence to support
Terminology
We are interested in creativity. We believe people that are awake at night (and sleep during the day) are more creative than those that are awake during the day (and sleep at night). We collect a sample of 30 people from across the country, 15 of those people are awake at night, and 15 of those people are awake during the day.
What is the research hypothesis?
What is the null hypothesis?
Terminology
Something that is the same for everyone is C_______
Something that can take-on one or more values is a V_______
2X + 8, X is a _______
Person A’s height is a _______
Person A’s gender is a _______
Person A’s name is a _______
Is “4” a variable?
Is “male” a variable?
Terminology
What is the difference between an Independent Variable and a Dependent Variable?
Independent Variable (IV) a variable that can be manipulated
Dependent Variable (DV) a variable that is expected to be influenced by the manipulated variable, measured but not manipulated
Terminology
We are interested in creativity. We believe people that are awake at night (and sleep during the day) are more creative than those that are awake during the day (and sleep at night). We collect a sample of 30 people from across the country, 15 of those people are awake at night, and 15 of those people are awake during the day.
What is the IV?
What is the DV?
Terminology
Extraneous Variables other variables that may influence the dependent variable but are not manipulated, stuff we are not interested in (nuisance variables)
Want to “control” extraneous variables
(Related to chance)
Terminology
We are interested in creativity. We believe people that are awake at night (and sleep during the day) are more creative than those that are awake during the day (and sleep at night). We collect a sample of 30 people from across the country, 15 of those people are awake at night, and 15 of those people are awake during the day.
What could be an extraneous variable?
Terminology
What is the difference between a Population and a Sample?
Population everyone (or thing) of interest
Sample part of the population
Terminology
We are interested in creativity. We believe people that are awake at night (and sleep during the day) are more creative than those that are awake during the day (and sleep at night). We collect a sample of 30 people from across the country, 15 of those people are awake at night, and 15 of those people are awake during the day.
What is the population?
What is the sample?
Terminology
What is the difference between a Statistic and a Parameter?
Statistic a value describing a sample
Parameter a value describing the population
Terminology
Sample - Statistic Population - Parameter
Estimate statistics used to approximate parameters
Scales of Measurement
Scales of measurement different classes of variables
Nominal groups (gender, ethnicity, etc.)
Scales of Measurement
Ordinal groups, but there is an order (class level)
Interval numbers with an equal distance between each value (Likert scale)
Scales of Measurement
Ratio numbers with an equal distance between each value AND zero means absence (height, salary, age, etc.)
Scales of Measurement
Which are rankings (1st 2nd 3rd …)? Why?
Which is temperature Fahrenheit?
Which is temperature Celsius?
Which is temperature Kelvin?
Are negative numbers allowed for ratio variables?
Which is your net worth?
What is required to be ratio?
Scales of Measurement
Why do these scales matter?
To say “twice as much” Ratio To say “5 points more” Interval (or
Ratio) To say “more” Ordinal (or Interval or
Ratio) Can only say “different” with Nominal
Scales of Measurement
Ratio holds the most info… and we can always “downgrade” ratio into any of the other types
Also influences the statistics we can calculate (mean, standard deviation) and tests we can perform (t, regression, ANOVA, Chi-Square…)
Scales of Measurement
Nominal and ordinal are collectively called categorical or qualitative
Interval and ratio are collectively called continuous or quantitative
Symbols & Math
Symbols
What is PEMDAS?
How should we round 2.48276?
257.469?
13.795218?
4?
*Critical values and probabilities*
Review
What is a hypothesis?
Give an example of a null and research hypothesis
Review
What is an independent variable?
What is a dependent variable?
What is an extraneous variable?
Review
What is the relationship between populations, samples, statistics and parameters?
What is an estimate?
Review
Give an example of a variable measured on a nominal scale
An ordinal scale
An interval scale
A ratio scale
Preview
Today we talked about Statistics in general and defined some key terms
Next time we will talk about graphing and organizing data