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12 Cards in this Set
- Front
- Back
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What is central tendency, and what are the three measures?
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A part of descriptive statistics-
It summarizes information about the most typical, central, or common scores of a variable. It summarizes the dsitribution of scores as a single number. Mean, Median, and Mode |
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What is mode?
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the most common , the most common single number in a distribution. ti can be used with variables at all three levels of measurement. it is most often used with nominal level variables.
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What is median?
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the score of the middle case. that can be used with variables measured at the ordinal or interval-ratio levels. it cannot be used for nominal-level variables.
**if yu have an even number of values, the median is the average score of the two middle cases |
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What is mean?
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the average score. used with equal-interval variables.
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What are characteristics of the mean?
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all scores cancel out around the mean
the mean is the point of minimized variation the mean uses all of the scores |
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What are the strengths and weaknessess of the mean?
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Strengths: the mean uses all information available from the variable.
Weaknesses: the mean is affected by every score, if there are some very high or low scores, the mean may be misleading. |
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How do mean, median, and skew come together?
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When a distribution has a few very high or low scores, the mean will be pulled in the direction of the extreme scores.
When an interval-ratio variable has a pronounced skew, the median may be the more trustworthy measure of central tendency. |
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For a positive skew, will the mean be greater or less than the median?
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greater than
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For a negative skew will the mean be greater or less than the median?
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less than
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When do you use the mode?
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1. variables are measured at the nominal level
2. you want a quick and easy measure for ordinal and interval-ratio variables. 3. you want to report the most common score. |
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When do you use median?
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1. variables are measured at the rank-order (ordinal) level
2. variables measured at the interval-ratio level have highly skewed distributions 3. when a distribution has one or more outliers 4. you want to report the central score. the median always lies at the exact center of a distribution. |
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When do you use mean?
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1. variables are measured at the interval-ratio level (except for highly skewed distributions)
2. you want to report the typical score. the mean is 'the fulcrum that exactly balances all of the scores" 3. you anticipate additional statistical analysis |
