How do researchers maintain their objectivity concerning a study and its results?

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How do researchers maintain their objectivity
concerning a study and its results?

• Studying representative samples
• Through statistics

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Statistical Reasoning
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Statistical Reasoning
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Purposes of Statistics

• Summarize or describe data
• Compare individuals or groups of individuals in
  various ways
• Determine whether certain aspects of behavior are
  related
• Predict future behavior from current information

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Psychologists basically use two kinds of
statistics in their research

• Descriptive statistics
• Inferential statistics

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Descriptive Statistics (summarizing the data)

• Frequency distribution
• Central tendency
• Dispersion

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Frequency Distribution

• Indicates the number of times each score occurs
  within an entire set of scores

• Person 1 1
• Person 2 2
• Person 3 3
• Person 4 3
• Person 5 4
• Person 6 4
• Person 7 4
• Person 8 5
• Person 9 6

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Graphing Frequency Distribution
Frequency of Each Stare
1 2 3 4
5 6
Number of Seconds until Recipient of Stare Looks
Away or Approaches Starer
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Measures of Central Tendency

• An index of the middle score of the distribution
  of scores
• Mean
• Median
• Mode

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Mean (arithmetic average)

• Add all scores and then divide by the total
  number of scores
• Represents the typical score
• Strongly affected by extreme scores

• 1
• 2
• 3 45/ 9 5
• 3
• 4 Mean 5
• 4
• 4
• 5
• 19
• 45

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Mode

• Most frequently occurring score

• 1
• 2 Mode 4
• 3
• 3
• 4
• 4
• 4
• 5
• 19

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Median

• The midpoint of the distribution
• 50 of scores fall at or above the median, while
  50 fall at or below this value

• 1
• 2
• 3 Median 4
• 3
• 4 ?
• 4
• 4
• 5
• 19

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Measures of Dispersion

• Indicate the shape of the distribution of scores
• Range
• Variance
• Standard Deviation

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Range

• The difference between the highest and lowest
  scores
• Does not indicate how much scores spread out
  around the center

• 1 19
• 2 - 1
• 3 18
• 3
• 4 Range 18
• 4
• 4
• 5
• 19

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Variance

• D D2
• 1 - 5 -4 -4 16
• 2 - 5 -3 -3 9
• 3 - 5 -2 -2 4
• 4 - 5 -1 -1 1
• 4 - 5 -1 -1 1
• 4 - 5 -1 -1 1
• 5 - 5 0 0 0
• 6 - 5 1 1 1
• 19 - 5 14 14 196
• 229
• 229/9 25.44
• Variance 25.44

• The averaged squared distance between each score
  and the mean

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Distribution of Scores
Frequency of Each Score
Number of Seconds until Recipient of Stare Looks
Away or Approaches Starer
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Standard Deviation

• Square root of the sum of the squared deviations
  from the mean divided by the number of scores
• Indicates the degree to which individuals within
  between groups differ from each other
• Better gauges whether scores are packed together
  or dispersed because it uses information from
  each score

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Standard Deviation
D D2
1 - 5 -4 ? -4 16 229 ? 9
25.44 2 - 5 -3 -3 9
Variance 25.44 3 - 5 -2 -2
4 4 - 5 -1 -1 1 4 - 5
-1 -1 1 4 - 5 -1 -1
1 5 - 5 0 0 0 6 - 5 1
1 1 19 - 5 14 14 196
229
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The Normal Curve
99.7
95
68
Number of Scores
-3 -2 -1 0 1
2 3 IQ 55 70 85 100
115 130 145
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Inferential Statistics

• Help researchers evaluate the reliability or
  trustworthiness of the conclusions they derive
  from their research
• Help determine whether the difference between
  groups is meaningful or whether the difference is
  one that could have occurred by chance

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Meaningfulness of Results

• Determined by a criterion called statistical
  significance
• Differences between groups that are considered to
  be statistically significant are differences in
  which there is less than 5 chances in 100 that
  they could be due to chance alone