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1 NURS/HSCI 597 Frequency Distribution Heibatollah Baghi, and Mastee Badii

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2 Nominal-Level data is merely descriptive (e.g. religion, country name, region). Any assigned numerical value is merely for convenience (e.g. Christian = 1, Jewish = 2, Buddhist = 3) Ordinal-Level data has rank order, though intervals between data points cannot be considered equal (e.g. high/medium/low income, GDP/capita rank, HDI rank) Interval-Level data has equal intervals between data points Ratio-Level data has equal intervals between data points and a true zero Levels of Measurement

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3 Table 1: Grades from 50 Students

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4 1.Sort the data 2.Tally the data (mutually exclusive and collectively exhaustive) 3.Sum the tally (Sum of frequencies = sample size) Ungrouped Frequency Distribution of Heart Rates 606563576465 707268646266 566967736863 606661606567 657266586260

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5 Ungrouped Frequency Distribution of Heart Rate Scores ScoreFrequencyScoreFrequency 561654 571663 581672 590682 604691 611701 622710 632722 642731 Sum30

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6 Frequency Percentages & Cumulative Percentages % = (f / N) * 100 Percentage = First divide frequency by sample size and then multiply by 100 Cumulative percentage shows the percentage of scores that are equal to or lesser than a specified score.

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7 SPSS Steps for Frequency Distribution 1. Read data into SPSS 2. Select from Analyze 3. Select variable & press OK 3. Get results

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8 Heart Rate Frequency Distribution

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9 Choose the Type of Chart that Best Describes a Variable Characteristic Bar chart is used for Nominal or Ordinal data –Pie chart is an alternative to the bar chart Histogram is appropriate for interval ratio –Polygon is equivalent to histogram but appear smoother

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10 Bar Graph Works for Nominal or Ordinal data Consists of a horizontal (X-axis) and vertical dimension (Y-axis) Categories are along the X-axis Frequencies or percentages are displayed on Y-axis SPSS can draw a bar graph for you

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11 SPSS Steps: Recode for Bar Chart 2. Select variable 3. Rename 4. Indicate changes 5.Show range 6. Show new values & add 1. Select to recode 7. Heart rate recoded into 3 categories

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12 SPSS Steps: Bar Chart 1. Follow steps for Frequency Distribution 2. Select chart 3. Select bar chart 4. See results

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13 Bar Chart for Heart Rate Categories

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14 Histograms(Grouped Frequency Distribution) Used for interval or ratio level data X-axis shows the categories, next to each other Y-axis shows the frequency or relative frequency Histograms are grouped-data frequency distributions

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15 Histogram for Student Grades 1.Find the lowest and highest score 2.Find the range of scores 3.Decide on the number of intervals (e.g., 5) 4.Divide the range by number of intervals 5.Determine the lowest class interval 6.List all class intervals. 7.Tally the number of scores that fall in each class interval. 8.Convert each tally to a frequency.

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16 Histogram of Student Grades The lowest score and highest score (51,99) The range of scores (99 – 51 = 48) Number of intervals (5) Range (48 / 5 ~ 10) Lowest class interval (51-60) All class intervals 51-60,61-70,71- 80,81-90,91-100 Tally the number of cases that fall within each interval Frequency counts: 2,9,14,21,4

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17 SPSS Steps: Histogram 1. Follow steps for Frequency Distribution 2. Select chart 3. Select histogram 4. See results

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18 Histogram of Student Grades

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19 Characteristics of Frequency Distributions Central Tendency –Mean –Median Variability –Range –Standard deviation Shape (Normal, Bimodal, Skewed, J- Shaped, Kurtosis)

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20 Normal

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21 Bi-modal

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22 Negatively skewed

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23 Positively skewed

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24 J-shaped

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25 Rectangular

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26 Platykurtic

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27 Take Home Lesson Data can be described by the central tendency, variability and shape of the frequency distribution

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