Lecture 3 Outline of Last Lecture I Intro to Statistics II Population and samples III Types of Statistics IV Defining and Measuring Variables V Constructs and Operational Definitions Outline of Current Lecture I Scales of Measurement II Review of Mathematical Operations III Symbols IV Descriptive Statistics V Frequency Distributions Current Lecture I Scales of Measurement Psych 311 1nd Edition allows us to quantify constructDiscrete Categorical Variable separate categories are used to quantify HOW MANY Continuous Variables variables with the property that between any two values there are an infinite number of other values used to quantify HOW MUCH Four Scales of Measurement Normal Ordinal Interval Ratio least most sophisticated more sophisticated gives more info Nominal categorical variable set of categories with different names none are better or worse than another measurement doesn t make any quantitative distinction ex gender major etc only receivable info how many are in each category can t organize or make calculations Ordinal continuous variable sometimes categorical has same qualities as nominal scale but with added dimension of ordering measurements are ranked observations in terms of size or magnitude ranked order intervals between categories are uneven or unequal These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best ex olympic metals are listed 1st 2nd 3rd but you don t know by how much continuous because can rank variables Interval continuous variable has same qualities as ordinal scale but with added dimension of same size intervals equal differences between the numbers on of this scale reflect equal differences in magnitude zero doesn t equal absence of variables ex 1 2 3 4 5 vs 2 1 0 1 2 most psychological characteristics measured by this interval scale temperature measured on interval scale 0 degrees is still a temp Ratio continuous variable has same qualities as interval scale but with added dimension of true zero 0 absence of variable ex recording number of absences per student within a semester most observable behaviors can be measured on ratio scale II Review of Mathematical Operations PEMDAS Calculations within Parentheses Exponenets e g squaring Multiplying Dividing from left to right Addition Subtraction is last from left to right Summation sum all the numbers Data X 5 8 3 9 X sum of all X s 5 8 3 9 25 X sum of all X 5 8 3 9 179 X sum all X s then square it 5 8 3 9 25 25 625 III Symbols symbols should tell you something different sets of symbols for population and samples Stats Population Sample Size n Mean M Variance s Standard Deviation SD s IV Descriptive Statistics statistical procedures used to summarize organize and simplify data should be able to look at descriptive stats and get general idea of whole set averages are descriptive stats gives sense about population ways of describing data graphs measures of central tendency measures of variability V Frequency Distributions graphs or organized tabulation of number of individuals located in each category on scale or measure tallying up numbers within category frequency table shows how often each value of variable occurs f N X f a 5 b 3 c 7 Finding X Xf Xf fX Proportions and Percentages p f N p 100 Frequency Distribution Graphs y axis is the frequency you can have a frequency of zero x axis is the catagory