Week 9 - Descriptive Statistics Flashcards

1
Q

Uses for descriptive statistics

A
  1. Descriptive Studies
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2
Q

Descriptive studies- what do they do in a set of data

A

characterize shape, central tendency and variability within a set of data

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3
Q

what is the purpose of descriptive studies

A

describe a sample or population

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4
Q

population measures in a descriptive study

A

parameters

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5
Q

Sample measures in a descriptive study

A

statistic
- statistics are used to estimate population parameters

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6
Q

Distribution of data

A
  • readiness for statistical testing
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7
Q

what do you need to know for distribution of data

A
  1. central point around which data tends to cluster (average)
    - measure of central tendency
    - “typical value in the set of observations
  2. how far from central point all data lies
    - variability
  3. examine visual display of scores
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8
Q

Frequency of distribution

A

distribution
- total set of scores for a variable
- N=total # of scores in distribution
- summarize data with frequency of distribution; a table of rank ordered scores and frequency of each

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9
Q

How can you graph frequency of distribution

A
  1. histogram
  2. line plot
  3. stem and leaf plot
  4. distribution shape: skewed right/positively skewed or skewed left/negatively skewed
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10
Q

Central tendency: mean

A
  • arithmetic average
  • can be influenced by extreme values
  • sample mean: x̄
  • population mean:μ
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11
Q

Central tendency: median

A
  • middle score of distribution
    1. put data points in order select middle data point
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12
Q

Central Tendency mode

A
  • score that occurs most frequently in distribution
  • blue
  • most for categories
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13
Q

Measure of variability

A
  1. Range: difference between highest and lowest values of distribution
  2. percentiles: describe scores position within distribution
    - convert scores into comparative scores
  3. quartiles: divide distribution into 4 quarters
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14
Q

Box and whisker plots

A
  • box: interquartile range (between 1st and 3rd quartile)
  • whiskers: range of scores
  • horizontal line: 50th percentile = median
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15
Q

Coefficient of variation

A
  • ratio of standard deviation to mean
  • expressed as %
  • can compare between different types of measures, between different distribution
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