Psyc_315_-Winter_2010_-_Class_2

Psyc_315_-Winter_2010_-_Class_2 - Recap of Last Week...

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1 Recap of Last Week • Descriptive vs. Inferential Statistics • Population vs. Sample • Parameter vs. Statistic • Independent vs. Dependent Variable • Qualitative vs. Quantitative Variable • Discrete vs. Continuous Variable • Levels of Measurement 2 Recap of Last Week Level Defining Aspects Example Nominal Non-numeric variable; values are categories Gender, religion, Living situation Rank-Order Numeric variable; values are relative rankings Class standing, place in race Equal-Interval Numeric variable; differences between values correspond to differences in thing being measured Celsius scale, self- report measures (e.g., on stress) Ratio Numeric variable; same as Interval AND ratios of magnitudes are meaningful Kelvin scale, length, weight Frequency Distributions
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4 Frequency Distribution • Individual scores provide some information, but awkward to interpret and manipulate when there is large amount of data. • Example: – Your score of 76 in a class that is made up of 5 or 30 students. – How many got lower, higher or the same score as you? Score 90 76 54 85 42 85 34 98 50 42 53 90 76 68 87 45 71 82 54 29 76 63 57 96 31 5 Frequency Distribution • Raw data can, therefore, be reorganized to facilitate interpretation. • This is done by using: – Frequency Distribution Tables – Frequency Distribution Graphs • Scores are listed in rank order, along with their frequency of occurrence. • Make any pattern of numbers clear at a glance. 6 Ungrouped Frequency Table Reorganize values from highest to lowest. 6 3 4 6 8 5 7 9 9 6 8 7 4 5 2 10 7 1 7 8 10 9 9 8 8 8 7 7 7 7 6 6 6 5 5 4 4 3 2 1
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7 Frequency • Tally the raw scores into frequencies (f). • Even if no one got a certain score include it in the table. • Calculate the sum ( N ) s N = f s N = 1 + 2 + 3 + 4 + 3 + 2 + 0 + 2 + 2 + 1 s N = 20 • Note: is Sum Score f 10 1 9 2 8 3 7 4 6 3 5 2 4 0 3 2 2 2 1 1 0 0 N = 20 8 Relative Frequency • Relative Frequency: s P roportion (or ratio) of times each score occurs over total number of scores. s Relative f = f / N s Note: will always be 1.0 Score f Relative f 10 1 . 05 9 2 . 10 8 3 . 15 7 4 . 20 6 3 . 15 5 2 . 10 4 0 0/20=0 3 2 2/20= . 10 2 2 2/20= . 10 1 1 1/20= . 05 0 0 0 N = 20 = 1.0 9 Percentage By multiplying the relative frequency by 100 you obtain the percentage (%) of times each score occurs over total number of scores. • Note: will always be 100. • E.g.: 10% of students obtained a score of 9. Score f Relative f % 10 1 . 05 5 9 2 . 10 10 8 3 . 15 15 7 4 . 20 20 6 3 . 15 15 5 2 . 10 10 4 0 0 0 3 2 . 10 10 2 2 . 10 10 1 1 . 05 5 0 0 0 0 N = 20 = 1.0 = 100
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10 Ungrouped Frequency Tables Score f Relative f % 10 1 .05 5 9 2 .10 10 8 3 .15 15 7 4 .20 20 6 3 .15 15 5 2 .10 10 4 0 0 0 3 2
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Psyc_315_-Winter_2010_-_Class_2 - Recap of Last Week...

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