Jaymie Ticknor Quantitative Methods 2317 Sect 001 15 January 2014 Tutors Lecture 1 Alex Bach Monday 8 10am 12 1pm Tuesday 8 9 30am Wednesday 8 9am 11am 1pm Thursday 8 9 30am Friday 8 9am Allyson Sharf office upstairs Monday 10 45am 12 45pm 4 5pm Tuesday 2 4pm Wednesday 2 5pm Thursday 3 5pm Displaying the Order in a Group of Numbers Chapter 1 Two Branches of Statistical Methods Descriptive summarize and describe a group of numbers from a research study Inferential draw conclusions and make predictions Basic Concepts Variable any characteristic or condition that can change vary gender age Value possible number or category a score can have male female transgender 0 100 Score a particular person s value female 86 Levels of Measurement Equal Interval variable in which the numbers stand for approximately equal amounts of what is being measured GPA difference between 2 3 and 4 0 difference between 1 7 and 3 4 depression scores on BDI difference between 5 and 7 difference between 2 and 4 Ratio special case of equal interval contains a true zero point value of zero absence of the thing being measured grades number of siblings distance time weight Rank Ordered Variable Ordinal values correspond to number of things being measured standing in graduating class Valedictorian 530th place in a race 1st 2nd 3rd birth order Nominal Variable Categorical names or categories gender diagnosis PTSD Schizophrenia Ethnicity European American African American Latino a Continuous possible to have an infinite number of values between two intervals height no way to measure every possible inch foot centimeter age you could be 26 932210 years old Discrete values that have no other values between them number of siblings nominal variables gender religion etc Frequency Tables Table that shows how many times each score is used Nominal data taco burger football team Steps make a list of each possible value from lowest to highest go through scores making a mark for each value next to it make a table showing how many times each value is used calculate percentage of scores for each value Can be used for nominal variables can group intervals of variables together Histograms Height of each bar is the frequency of each value in the frequency table when you have a nominal variable the histogram is called a bar graph Steps make a frequency table put the values along bottom of the page left to right highest to lowest make a scale of frequencies on the left side of the page from 0 to highest frequency for any value make a bar for each value with a height for the frequency of that value Shapes of Frequency Distributions Unimodal one high area hump Bimodal two fairly high points humps Rectangular Uniform values all have about the same frequency Symmetrical left and right side of distribution are mirror images Skewed score pile up on one side of the distribution not symmetrical The side with fewer scores tail is the direction of the skew skewed to the right positive skewed to the left negative Normal Curve distribution that is bell shaped symmetrical unimodal and mesokurtic Kurtosis how much curve differs from normal curve in terms of more peaked and more flat General Forms Leptokurtic positive highest peak more common Mesokurtic normal and Platykurtic negative low peak less common Misleading Graphs failure to use equal interval sizes population data exaggeration of proportions start at 0 to see actual proportions